Antibody binding to fcrn for treating autoimmune diseases

ABSTRACT

The present disclosure relates to an isolated anti-FcRn antibody, which is an antibody binding to FcRn (stands for neonatal Fc receptor, also called FcRP, FcRB or Brambell receptor) that is a receptor with a high affinity for IgG or a fragment thereof, a method of preparing thereof, a composition for treating autoimmune disease, which comprises the antibody, and a method of treating and diagnosing autoimmune diseases using the antibody. The FcRn-specific antibody according to the present disclosure binds to FcRn non-competitively with IgG to reduce serum pathogenic auto-antibody levels, and thus can be used for the treatment of autoimmune diseases.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part under 35 USC §120 of U.S.patent application Ser. No. 15/301,948 filed Oct. 4, 2016 for ANTIBODYBINDING TO FCRN FOR TREATING AUTOIMMUNE DISEASES, which is in turn aU.S. national phase under the provisions of 35 U.S.C. §371 ofInternational Patent Application No. PCT/KR15/04424 filed Apr. 30, 2015,which in turn claims the benefit of U.S. Provisional Patent ApplicationNo. 61/986,742 filed Apr. 30, 2014. The disclosures of all such patentapplications are hereby incorporated herein by reference in theirrespective entireties, for all purposes.

TECHNICAL FIELD

The present disclosure relates to an isolated anti-FcRn antibody, whichis an antibody binding to FcRn (stands for neonatal Fc receptor, alsocalled FcRP, FcRB or Brambell receptor) that is a receptor with a highaffinity for IgG or a fragment thereof, a method of preparing thereof, acomposition for treating autoimmune disease, which comprises theantibody, and a method of treating and diagnosing autoimmune diseasesusing the antibody. The FcRn-specific antibody according to the presentdisclosure binds to FcRn non-competitively with IgG to reduce serumpathogenic auto-antibody levels, and thus can be used for the treatmentof autoimmune diseases.

BACKGROUND

Antibodies are immunological proteins that bind to a specific antigen.In most animals, including humans and mice, antibodies are constructedfrom paired heavy and light polypeptide chains and each chain is made upof two distinct regions, referred to as the variable and constantregions. The light and heavy chain variable regions show significantsequence diversity between antibodies, and are responsible for bindingthe target antigen. The constant regions show less sequence diversity,and are responsible for binding a number of natural proteins to elicitimportant biochemical events.

Under normal conditions, the half-life of most IgG excluding IgG3isotype in serum is about 22-23 days in humans, which is a prolongedperiod relative to the serum half-life of other plasma proteins. Withrespect to this prolonged serum half-life of IgG, IgG that entered cellsby endocytosis can strongly bind to neonatal Fc receptor (FcRn, a kindof Fc gamma receptor) in endosomes at a pH of 6.0 to avoid thedegradative lysosomal pathway. When the IgG-FcRn complex cycles to theplasma membrane, IgG dissociates rapidly from FcRn in the bloodstream atslightly basic pH (˜7.4). By this receptor-mediated recycling mechanism,FcRn effectively rescues the IgG from degradation in lysosomes, therebyprolonging the half-life of IgG (Roopenian et al. J. Immunol. 170:3528,2003).

FcRn was identified in the neonatal rat gut, where it functions tomediate the absorption of IgG antibody from the mother's milk andfacilitates its transport to the circulatory system. FcRn has also beenisolated from human placenta, where it mediates absorption and transportof maternal IgG to the fetal circulation. In adults, FcRn is expressedin a number of tissues, including epithelial tissues of the lung,intestine, kidney, as well as nasal, vaginal, and biliary tree surfaces.

FcRn is a non-covalent heterodimer that typically resides in theendosomes of endothelial and epithelial cells. FcRn is a membrane boundreceptor having three heavy chain alpha domains (α1, α2 and α3) and asingle soluble light chain β2-microglobulin (β2m) domain. Structurally,it belongs to a family of major histocompatibility complex class 1molecules that have β2m as a common light chain. The FcRn chain has amolecular weight of about 46 kD and is composed of an ectodomaincontaining the α1, α2, and α3 heavy chain domains and a β2m light chaindomain and having a single sugar chain, a single-pass transmembrane, anda relatively short cytoplasmic tail.

In order to study the contributions of FcRn to IgG homeostasis, micehave been engineered so that at least part of the genes encoding β2m andFcRn heavy chains have been “knocked out” so that these proteins are notexpressed. In these mice, the serum half-life and concentrations of IgGwere dramatically reduced, suggesting an FcRn-dependent mechanism forIgG homeostasis. It has also been suggested that anti-human FcRnantibodies may be generated in these FcRn knockout mice and that theseantibodies may prevent the binding of IgG to FcRn. The inhibition of IgGbinding to FcRn negatively alters IgG serum half-life by preventing IgGrecycling, so that autoimmune diseases caused by auto-antibodies can betreated. This possibility was shown in a mouse model of autoimmunecutaneous bullous diseases (Li et al. J. Clin. Invest. 115:3440, 2005).Accordingly, agents that block or antagonize the binding of IgG to FcRnmay be used in a method for treating or preventing autoimmune andinflammatory diseases, which are mediated by IgG.

“Autoimmune diseases” cover diseases that occur when the body's immunesystem attacks its own normal tissues, organs or other in vivocomponents due to immune system abnormalities whose cause cannot befound. These autoimmune diseases are systemic diseases that can occur inalmost all parts of the body, including the nervous system, thegastrointestinal system, the endocrine system, the skin, the skeletalsystem, and the vascular tissue. It is known that autoimmune diseasesaffect about 5-8% of the world population, but the reported prevalenceof autoimmune diseases is lower than the actual level due to limitationsin the understanding of autoimmune diseases and a method for diagnosingthese diseases.

The causes of autoimmune diseases have been studied for a long period oftime in terms of genetic, environmental and immunological factors, buthave not yet been clearly identified. Many recent studies revealed thata number of autoimmune diseases are caused by IgG-type autoantibodies.In fact, the relation between the presence or absence ofdisease-specific autoantibodies and the treatment of autoimmune diseaseshas been widely identified from studies on the disease and the treatmentof autoimmune diseases. Thus, the presence of disease-specificautoantibodies and the pathological role thereof in a large number ofautoimmune diseases have been identified, and when the autoantibodies ofinterest are removed from blood, an effect of quickly treating diseasescan be obtained.

Autoimmune diseases and alloimmune diseases are mediated by pathogenicantibodies, and typical examples thereof include immune neutropenia,Guillain-Barré syndrome, epilepsy, autoimmune encephalitis, Isaac'ssyndrome, nevus syndrome, pemphigus vulgaris, Pemphigus foliaceus,Bullous pemphigoid, epidermolysis bullosa acquisita, pemphigoidgestationis, mucous membrane pemphigoid, antiphospholipid syndrome,autoimmune anemia, autoimmune Grave's disease, Goodpasture's syndrome,myasthenia gravis, multiple sclerosis, rheumatoid arthritis, lupus,idiopathic Thrombocytopenic Purpura (ITP), lupus nephritis or membranousnephropathy, or the like.

For example, it is known that, in case of myasthenia gravis (MG),acetylcholine receptor (AChR) located at the neuromuscular junction ofvoluntary muscles is destroyed or blocked by autoantibodies against thereceptor to impair the function of voluntary muscles. Also, it is knownthat when such autoantibodies are reduced, the function of muscles isrestored.

As to the case of ITP, ITP is a disease caused by the destruction ofperipheral platelets due to the generation of auto-antibodies that bindto a specific platelet membrane glycoprotein. Anti-platelet antibodiesopsonize platelets and result in rapid platelet destruction by reticularcells (e.g., macrophages).

In general, attempts to treat ITP include suppressing the immune system,and consequently causing an increase in platelet levels. ITP affectswomen more frequently than men, and is more common in children thanadults. The incidence is 1 out of 10,000 people. Chronic ITP is one ofthe major blood disorders in both adults and children. It is a source ofsignificant hospitalization and treatment cost at specializedhematological departments in the US and around the world. Each yearthere are approximately 20,000 new cases in the US, and the cost for ITPcare and special therapy is extremely high. Most children with ITP havea very low platelet count that causes sudden bleeding, with typicalsymptoms including bruises, small red dots on the skin, nosebleeds andbleeding gums. Although children can sometimes recover with notreatment, many doctors recommend careful observation and mitigation ofbleeding and treatment with intravenous infusions of gamma globulin.

It is known that the important pathogenesis of Lupus nephritis, a kindof autoimmune disease, is that an increased immune complex, which couldbe occurred due to the inappropriate overproduction of auto-antibodiessuch as anti-nuclear antibodies, is accumulated in the systemic organsto cause inflammatory responses. About 40-70% of Lupus patients haverenal involvement, and about 30% of the patients develop Lupusnephritis, which is known as a bad prognostic factor in Lupus patients.Although methods of treating Lupus nephritis using immunosuppressiveagents have been attempted, it was reported that remission was notinduced in about 22% of Lupus nephritis patients even whenimmunosuppressive agents were used. Also, it was reported that, evenwhen remission was induced, 10-65% of patients relapsed into Lupusnephritis when the use of immunosuppressive agents was reduced.Ultimately, 5-10% of patients with serious Lupus nephritis (WHO classIII and IV) die after 10 years, and 5-15% of the patients lead toend-stage renal stage. Thus, appropriate treatment of Lupus nephritishas not yet been reported.

Thus, the use of antibodies having a new mechanism that treat autoimmunediseases by clearing pathogenic autoantibodies is expected to havetherapeutic effects against pathogenic IgG-mediated autoimmune diseasessuch as pemphigus vulgaris, neuromyelitis optica and myasthenia gravis,as well as immune complex-mediated glomerular diseases such as Lupusnephritis or membraneous nephropathy.

Methods of treating autoimmune diseases by intravenous administration ofIgG (IVIG) in large amounts have been widely used (Arnson Autoimmunity42:553, 2009). IVIG effects are explained by various mechanisms, but arealso explained by the mechanism that increases the clearance ofpathogenic antibodies by competition with endogenous IgG for FcRn.Intravenous administration of human immunoglobulin (IVIG) in largeamounts has been shown to increase platelet counts in children afflictedwith immune ITP, and IVIG has shown to be beneficial as a treatment forseveral other autoimmune conditions. Many studies have investigated themechanisms by which IVIG achieves effects in the treatment of autoimmunediseases. With regard to ITP, early investigations led to the conclusionthat IVIG effects are mainly due to blockade of the Fc receptorsresponsible for phagocytosis of antibody-opsonized platelets. Subsequentstudies showed that Fc-depleted IVIG preparations provided increases inplatelet counts in some patients with ITP, and recently it was reportedthat IVIG effects are due to stimulation of FcγRIIb expression onmacrophage cells, leading to inhibition of platelet phagocytosis.

However, such IVIG treatments have substantial side effects and are verycostly to administer. Further, other therapies used for the treatment ofautoimmune/alloimmune conditions other than IVIG include polyclonalanti-D immunoglobulin, corticosteroids, immuno-suppressants (includingchemotherapeutics), cytokines, plasmapheresis, extracorporeal antibodyadsorption (e.g., using Prosorba columns), surgical interventions suchas splenectomy, and others. However, like IVIG, these therapies are alsocomplicated by incomplete efficacy and high cost. Also, very high dosesof IVIG are required to produce substantial increases in the clearanceof pathogenic antibody due to the putative mechanism of IVIG inhibitionof FcRn binding with pathogenic antibody (i.e., competitive inhibition)and due to the fact that IgG shows very low affinity for FcRn atphysiologic pH (i.e., pH 7.2-7.4), and the typical clinical dose of IVIGis about 2 g/kg.

The use of an inhibitor that competitively inhibits the binding of IgGto FcRn to treat autoimmune diseases is a promising therapeutic method.However, owing to the high affinity of endogenous IgG for FcRn and tothe high concentrations of endogenous IgG in blood, it is likely thatcompetitive inhibition of FcRn would require very high doses, and thushave the same limitations similar to those of the current IVIGtreatment.

Accordingly, although the anti-FcRn antibody is disclosed inWO2006/118772, WO2007/087289, WO2009/131702, WO2012/167039, there is anurgent need for the development of an improved human antibody that has ahigh affinity for FcRn, and thus can remove pathogenic antibody even atlow doses and reduce immunogenicity.

DISCLOSURE OF INVENTION Technical Problem

The present inventors have made extensive efforts to solve theabove-described problems and to provide a medicament for effectively andfundamentally treating autoimmune disease including ITP, and finallyprovide an antibody that has a high affinity for FcRn or a fragmentthereof and a method of preparing the same. The antibody binding to FcRnor a fragment thereof, binds specifically to the FcRn chain in apH-independent manner and interferes non-competitively with the bindingof Fc of antibody to FcRn, to treat autoimmune disease by reducingautologous antibody in vivo, which could be a cause of autoimmunedisease.

It is an object of the present disclosure to provide a pharmaceuticalcomposition for treating autoimmune diseases, comprising the antibodybinding to FcRn, wherein the autoimmune disease is immune neutropenia,Guillain-Barré syndrome, epilepsy, autoimmune encephalitis, Isaac'ssyndrome, nevus syndrome, pemphigus vulgaris, Pemphigus foliaceus,Bullous pemphigoid, epidermolysis bullosa acquisita, pemphigoidgestationis, mucous membrane pemphigoid, antiphospholipid syndrome,autoimmune anemia, autoimmune Grave's disease, Goodpasture's syndrome,myasthenia gravis, multiple sclerosis, rheumatoid arthritis, lupus,idiopathic thrombocytopenic purpura, lupus nephritis or membranousnephropathy, or the like.

Technical Solution

To achieve the above objects, the present disclosure provides anisolated anti-FcRn antibody comprising:

CDR1 comprising one or more amino acid sequence selected from the groupconsisting of SEQ ID Nos: 21, 24, 27, 30, 33, 36, 39 and 42;

CDR2 comprising one or more amino acid sequence selected from the groupconsisting of SEQ ID Nos: 22, 25, 28, 31, 34, 37, 40 and 43; and

CDR3 comprising one or more amino acid sequence selected from the groupconsisting of SEQ ID Nos: 23, 26, 29, 32, 35, 38, 41 and 44, or afragment thereof.

Further, the present disclosure provides an isolated anti-FcRn antibodyor a fragment thereof comprising:

CDR1 comprising amino acid sequence, which has at least 90% homologywith one or more amino acid sequence selected from the group consistingof SEQ ID No: 21, 24, 27, 30, 33, 36, 39 and 42;

CDR2 comprising amino acid sequence, which has at least 90% homologywith one or more amino acid sequence selected from the group consistingof SEQ ID No: 22, 25, 28, 31, 34, 37, 40 and 43; and

CDR3 comprising amino acid sequence, which has at least 90% homologywith one or more amino acid sequence selected from the group consistingof SEQ ID No: 23, 26, 29, 32, 35, 38, 41 and 44.

Further, the present disclosure provides an isolated anti-FcRn antibodycomprising one or more heavy chain variable regions and light chainvariable regions comprising one or more amino acid sequences selectedfrom the group consisting of amino acid sequences of SEQ ID Nos: 2, 4,6, 8, 10, 12, 14, 16, 18 and 20.

Further, the present disclosure provides an isolated anti-FcRn antibodycomprising one or more heavy chain variable regions and light chainvariable regions comprising amino acid sequence, which has at least 90%homology with one or more amino acid sequences selected from the groupconsisting of amino acid sequences of SEQ ID Nos: 2, 4, 6, 8, 10, 12,14, 16, 18 and 20.

Further, the present disclosure provides an isolated anti-FcRn antibodyor a fragment thereof binding to an epitope of human FcRn comprisingresidues S15, S16, P17, P19, G20, A23, F24, S40, L41, R42, R69, E72,K73, F75, L76, F79, G84 and Y88 of α chain extracellular domain (SEQ IDNO:45) and E36 from β2m chain (SEQ ID NO:46)

Further, the present disclosure provides an isolated anti-FcRn antibodyor a fragment thereof binding to an epitope of human FcRn comprisingresidues S15, S16, P17, P19, G20, A23, F24, S40, L41, R42, R69, E72,K73, F75, L76, F79, G84 and Y88 of α chain extracellular domain (SEQ IDNO:45) and E36 from β2m chain (SEQ ID NO:46), wherein anti-FcRn antibodyor a fragment thereof binds to further one or more residues selectedfrom the group consisting of A13, V14, A18, T21, G43, K80, G83, K85 andG86 of α chain extracellular domain (SEQ ID NO:45)

Further, the present disclosure provides polynucleotide encoding theanti-FcRn antibody or a fragment thereof.

Further, the present disclosure provides polynucleotide encoding ananti-FcRn antibody comprising one or more sequence selected from thegroup consisting of SEQ ID Nos: 1, 3, 5, 7, 9, 11, 13, 15, 17 and 19.

Further, the present disclosure provides polynucleotide encoding ananti-FcRn antibody comprising sequence, which has at least 90% homologywith one or more sequence selected from the group consisting of SEQ IDNos: 1, 3, 5, 7, 9, 11, 13, 15, 17 and 19.

Further, the present disclosure provides a recombinant expression vectorcomprising the polynucleotide, host cell, which is transected with therecombinant expression vector. The present disclosure additionallyprovides a method of preparing an antibody binding specifically to FcRnor a fragment thereof comprising: culturing the host cell and producingthe antibody therefrom; and isolating and purifying the producedantibody to recover the anti-FcRn antibody.

Further, the present disclosure provides a pharmaceutical compositioncomprising the anti-FcRn antibody or a fragment thereof, and one or morepharmaceutically acceptable carrier.

Further, the present disclosure provides a method of treating a patientsuffering from an autoimmune disease, comprising administering thecomposition to said patient.

Further, the present disclosure provides a composition comprising theantibody labelled with a detection label.

Further, the present disclosure provides a method of detecting FcRn invivo or in vitro comprising using the anti-FcRn antibody or a fragmentthereof.

Advantageous Effects

The inventive antibody or a fragment thereof specific for FcRn that is areceptor having a high affinity for IgG has high affinity andspecificity, causes little or no immunogenicity-related problems, andbinds to FcRn non-competitively with IgG or the like to reduce serumauto-antibody levels. By virtue of such properties, the antibody or afragment thereof is useful for the treatment and diagnosis of autoimmunediseases.

BRIEF DESCRIPTION OF THE DRAWINGS

The patent or application file contains at least one drawing executed incolor. Copies of this patent or patent application publication withcolor drawing(s) will be provided by the Office upon request and paymentof the necessary fee.

FIG. 1 shows the results of analyzing the expression of antibodies inCHO-S cells and analyzing HL161A, HL161B, HL161C and HL161D antibodyproteins, obtained by protein A purification, on SDS-PAGE gel under areduced or non-reduced condition. It was shown that, under a non-reducedcondition, each of the HL161 antibodies had a whole human IgG1 typestructure having a size of about 160 kDa, and under a reduced condition,the heavy chain had a size of about 55 kDa, and the light chain had asize of about 25 kDa, suggesting that the antibody was composed oftypical antibody subunits. In FIG. 1, lane 1 represents a molecularweight (M.W.) marker, lane 2 represents 2 μg non-reduced (*NEM-treated)antibody, and lane 3 represents 2 μg reduced antibody.

FIGS. 2A through 2H show the results of analysis performed using a SPRsystem in order to determine the kinetic dissociation (KD) of four kindsof anti-FcRn antibodies (HL161A, HL161B, HL161C and HL161D) that bind toFcRn. The results in FIGS. 2A through 2H were obtained by analyzing theinteraction between human FcRn and the HL161A, HL161B, HL161C or HL161Dantibody at pH 6.0 and pH 7.4 using a Proteon GLC chip and a ProteonXPR36 (Bio-Rad) system, and more specifically:

FIG. 2A shows the results of analyzing the interaction between humanFcRn and the HL161A antibody at pH 6.0.

FIG. 2B shows the results of analyzing the interaction between humanFcRn and the HL161A antibody at pH 7.4.

FIG. 2C shows the results of analyzing the interaction between humanFcRn and the HL161B antibody at pH 6.0.

FIG. 2D shows the results of analyzing the interaction between humanFcRn and the HL161B antibody at pH 7.4.

FIG. 2E shows the results of analyzing the interaction between humanFcRn and the HL161C antibody at pH 6.0.

FIG. 2F shows the results of analyzing the interaction between humanFcRn and the HL161C antibody at pH 7.4.

FIG. 2G shows the results of analyzing the interaction between humanFcRn and the HL161D antibody at pH 6.0.

FIG. 2H shows the results of analyzing the interaction between humanFcRn and the HL161D antibody at pH 7.4.

FIG. 3 shows the ability of two selected antibodies to bind to the cellsurface, and shows the results obtained by treating humanFcRn-overexpressing HEK293 cells with selected HL161A and HL161Bantibodies binding to human FcRn present on the cell surface andanalyzing the antibodies binding to cell surface at pH 6.0 and pH 7.4.The binding of each of the HL161A and HL161B antibodies to human FcRnwas expressed as an MFI value obtained by performing fluorescentactivated cell sorter (FACS) using Alexa488-labelled anti-human goatantibody after treating cells with each antibody at varying pHs.

FIG. 4 shows the results of analyzing the ability to block the bindingof human IgG to human FcRn-expressing cells at pH 6.0, and shows theresults of observing whether two selected antibodies binding to cellsurface human FcRn can block the binding of human IgG to human FcRn, atthe cell level. A profile about the ability to block the binding ofAlexa488-labelled human IgG to human FcRn was obtained by diluting eachof HL161A and HL161B antibodies, confirmed to bind to humanFcRn-overexpressing HEK293 cells, serially 4-fold from 200 nM.

FIGS. 5A and 5B show the results of analyzing the effects of HL161A andHL161B antibodies, selected from human FcRn-expressing transgenic mouseTg32 (hFcRn+/+, hpβ2m+/+, mFcRn−/−, mpβ2m−/−), on the catabolism ofhIgG1. At 0 hour, 5 mg/kg of biotin-hIgG and 495 mg/kg of human IgG wereintraperitoneally administered to saturate IgG in vivo. Regarding drugadministration, at 24, 48, 72 and 96 hours after administration ofbiotin-IgG, IgG1, HL161A, HL161B or PBS was injected intraperitoneallyat doses of 5, 10 and 20 mg/kg once a day. Sample collection wasperformed at 24, 48, 72, 96, 120 and 168 hours after administration ofbiotin-IgG. At 24, 48, 72 and 96 hours, blood was collected before drugadministration, and the remaining amount of biotin-IgG was analyzed byan ELISA method. The results were expressed as the ratio of theremaining amount at each time point to 100% for the remaining amount inthe blood sample collected at 24 hours.

FIGS. 6A through 6C show the results of analyzing the change in bloodlevel of monkey IgG caused by administration of two antibodies (HL161Aand HL161B) to cynomolgus monkeys having a sequence homology of 96% tohuman FcRn. Each of HL161A and HL161B antibodies was administeredintravenously to cynomolgus monkeys at doses of 5 and 20 mg/kg once aday, and as a result, it was shown that monkey IgG decreased up to 70%compared to that at 0 hour, and decreased by about 30% up to day 29, andmore specifically:

FIG. 6A shows the serum IgG-reducing effects of HL161A and HL161Bantibodies at varying antibody concentrations.

FIG. 6B shows the serum IgG-reducing effects of HL161A and HL161Bantibodies (concentration: (5 mg/kg) in monkey individuals.

FIG. 6C shows the serum IgG-reducing effects of HL161A and HL161Bantibodies (concentration: (20 mg/kg) in monkey individuals.

FIGS. 7A and 7B show the results of analyzing the pharmacokineticprofiles of HL161A and HL161B in an experiment performed usingcynomolgus monkeys. It was shown that HL161B had a high half-life AUCand Cmax overall compared to HL161A.

FIGS. 8A through 8C show the results of analyzing the changes in bloodlevels of monkey IgM, IgA and albumin caused by administration of HL161Aand HL161B antibodies in an experiment performed using cynomolgusmonkeys. There were slight changes in the blood levels of monkey IgM,IgA and albumin, such changes were within the normal ranges ofcynomolgus monkeys, suggesting that such changes resulted from adifference between individuals rather than the influence of the testsubstances, and more specifically:

FIG. 8A shows a change in the serum IgM level of monkeys.

FIG. 8B shows a change in the serum IgA level of monkeys.

FIG. 8C shows a change in the serum albumin level of monkeys.

MODE FOR INVENTION

To achieve the above objects, the present disclosure provides anantibody, which can bind specifically to FcRn with high affinity in apH-independent manner and is composed of a human-derived sequence, andthus causes little or no immune response when administered in vivo.

Antibodies according to the present disclosure are binding moleculeshaving specificity for FcRn. The antibodies may include monoclonalantibodies (e.g., full-length antibodies having an immunoglobulin Fcdomain), antibody compositions with polyepitopic specificity, bispecificantibodies, diabodies, and single-chain molecules, as well as antibodyfragments (e.g., Fab, F(ab′)2 and Fv), but are not limited thereto. Theantibodies according to the present disclosure may be, for example,monoclonal antibodies against human FcRn.

The monoclonal antibodies include murine antibodies. Further, themonoclonal antibodies include “chimeric” antibodies in which a portionof the heavy and/or light chain is identical with or homologous tocorresponding sequences in antibodies derived from a particular speciessuch as mouse or belonging to a particular antibody class or subclass,while the remainder of the chain is identical with or homologous tocorresponding sequences in antibodies derived from another species orbelonging to another antibody class or subclass such as human, as wellas fragments of such antibodies, so long as they exhibit the desiredbiological activity. “Humanized antibodies” are used as a downstream setof “chimeric antibodies”.

As an alternative to humanization, human antibodies can be generated.“Human antibodies” are antibodies that are produced by humans or haveamino acid sequences corresponding to antibodies produced using anyhuman antibody production technology. Human antibodies can be producedusing various technologies known in the art, including phage displaylibraries. Human antibodies can be prepared by administering an antigento a transgenic animal that has been modified to produce such antibodiesin response to antigenic challenge, but whose endogenous loci have beendisabled, e.g., immunized xenomice. Antibodies according to the presentdisclosure may be in the form of, for example, human antibodies.

Native four-chain antibodies are heterotetrameric glycoproteins composedof two identical light (L) chains and two identical heavy (H) chains.Each light chain has a variable domain at one end (V_(L)) and a constantdomain at its other end. Each heavy chain has a variable domain (V_(H))at the N-terminus, and has three constant domains (CH) for α and γchains and four CH domains for μ and ε isotypes.

The term “variable” refers to the fact that certain portions of thevariable domains differ extensively in sequence among antibodies. The Vdomain mediates antigen binding and defines the specificity of aparticular antibody for its particular antigen. However, the variabilityis concentrated in three segments called hypervariable regions (HVRs)i.e. CDRs both in the light-chain and the heavy chain variable domains.The more highly conserved portions of variable domains are called theframework regions (FR). The light and heavy chain variable domainscomprise from N- to C-terminus the domains FR1, CDR1, FR2, CDR2, FR3,CDR3 and FR4.

In the present disclosure, antibodies having affinity and specificityfor human FcRn were obtained using human immunoglobulin transgenicanimals. Transgenic animals can be produced by inactivating animal Iggermline genes and transplanting human Ig germline gene loci. The use oftransgenic animals has an advantage in that an antibody is naturallyoptimized by the animal immune system without requiring affinitymaturation so that an antibody drug having low immunogenicity and highaffinity can be developed within a short time (US20090098134,US20100212035, Menoret et al, Eur J Immunol, 40:2932, 2010).

In the present disclosure, OmniRat™ (OMT, USA) having technologypatented for human immunoglobulin transgenic rats was used. OmniRat™ canefficiently select an antibody having a high affinity for human FcRn,because it has a heavy chain composed of CH2 and CH3 domains that arefrom rat genes, and V, D and J regions and CH1 domain that are fromhuman genes, and kappa light chain and lamda light chain from human, toefficiently select antibodies that have high affinity to human FcRn(Menoret et al, Eur J Immunol, 40:2932, 2010).

To obtain a monoclonal antibody having a high affinity for FcRn, atransgenic rat (OmniRat™) was immunized by injecting human FcRn therein,and then B cells were extracted from the cells and fused with myelomacells to generate a hybridoma, after which the produced antibody waspurified from the generated hybridoma.

The antibody according to the present disclosure acts as anon-competitive inhibitor of IgG in binding to FcRn. The binding of theantibody of the present disclosure to FcRn results in the inhibition ofpathogenic antibody to FcRn, which promotes the clearance (i.e.,removal) of pathogenic antibody from the body of the subject to reducethe half-life of the pathogenic antibody.

As used herein, the term “pathogenic antibody” means antibodies thatcause pathological conditions or diseases. Examples of such antibodiesinclude, but are not limited to, anti-platelet antibodies,anti-acetylcholine antibodies, anti-nucleic acid antibodies,anti-phospholipid antibodies, anti-collagen antibodies, anti-gangliosideantibodies, anti-desmoglein antibodies, etc.

As used herein, the term “epitope” or “specific residue” means the partof an antigen that is recognized by the antibody. The epitope for aantibody/antigen pair can be defined and characterized using a varietyof experimental and computational epitope mapping methods. Theexperimental methods include mutagenesis, X-ray crystallography, NuclearMagnetic Resonance (NMR) spectroscopy, Hydroged deuterium eXchange MassSpectrometry (HX-MS) and various competition binding methods.

The antibody or a fragment thereof according to the present disclosurehas an advantage in that it makes it possible to non-competitivelyinhibit the binding of pathogenic antibody to FcRn at physiological pH(i.e., pH 7.0-7.4). FcRn binds to its ligand (i.e., IgG) and does notsubstantially show affinity for IgG at physiological pH rather thanacidic pH. Thus, the anti-FcRn antibody that binds specifically to FcRnat physiological pH acts as a non-competitive inhibitor of the bindingof IgG to FcRn, and in this case, the binding of the anti-FcRn antibodyto FcRn is not influenced by the presence of IgG Thus, the inventiveantibody that binds to FcRn non-competitively with IgG in apH-independent manner has an advantage over conventional competitiveinhibitors (i.e., antibodies that bind to FcRn competitively with IgG)in that it can treat diseases even at significantly low concentrationsby the FcRn-mediated signaling of IgG. In addition, in the procedure ofintracellular migration in a state bound to FcRn, the anti-FcRn antibodyaccording to the present disclosure maintains its binding to FcRn withan affinity higher than IgG in blood, and thus can inhibit the bindingof IgG to FcRn even in endosomes that are acidic pH environments inwhich IgG can bind to FcRn, thereby promoting the clearance of IgG.

The antibody according to the present disclosure has an affinity forFcRn even in a physiological pH environment (i.e., pH 7.0-7.4) in whichIgG does not bind to FcRn. At a pH of 6.0, the antibody of the presentdisclosure has a higher affinity for FcRn compared to serum IgG,suggesting that it acts as a non-competitive inhibitor.

In an embodiment of the present disclosure, the present disclosure isdirected to an antibody binding specifically to FcRn or a fragmentthereof comprising:

CDR1 comprising amino acid sequence, which has at least 90% homologywith one or more amino acid sequence selected from the group consistingof SEQ ID No: 21, 24, 27, 30, 33, 36, 39 and 42;

CDR2 comprising amino acid sequence, which has at least 90% homologywith one or more amino acid sequence selected from the group consistingof SEQ ID No: 22, 25, 28, 31, 34, 37, 40 and 43; and

CDR3 comprising amino acid sequence, which has at least 90% homologywith one or more amino acid sequence selected from the group consistingof SEQ ID No: 23, 26, 29, 32, 35, 38, 41 and 44.

Those skilled in the art will appreciate that the deletion, addition orsubstitution of some amino acids in the amino acid sequences set forthin the above SEQ ID Nos. also falls within the scope of the presentdisclosure.

In addition, sequences having a homology to the nucleotide sequences andamino acid sequences set described in the present disclosure within acertain range also fall within the scope of the present disclosure.“Homology” refers to similarity to at least one nucleotide sequence oramino acid sequence selected from the group consisting of SEQ ID Nos: 1to 44, and include a homology of at least 90%. Preferably, homologymight be at least 91%, at least 92%, at least 93%, at least 94%, atleast 95%, at least 96%, at least 97%, at least 98% or at least 99%. Thehomology comparison is performed visually or using a known comparisonprogram such as BLAST algorithm with standard settings. A commerciallyavailable program can express the homology between two or more sequencesas a percentage. Homology (%) can be calculated for adjacent sequences.

Further, antibodies that bind specifically to FcRn having a KD(dissociation constant) of 0.01-2 nM at pH 6.0 and pH 7.4 also fallwithin the scope of the present disclosure. “KD” as used herein refersto equilibrium dissociation constant for antibody-antigen binding, andmay be calculated using the following equation: KD=kd/ka, wherein kaindicates association rate constant, and kd indicates dissociation rateconstant. The measurement of kd or ka can be performed at 25° C. or 37°C.

In one example, the antibody of the present disclosure comprises: CDR1comprising amino acid sequence of SEQ ID No: 21, CDR2 comprising aminoacid sequence of SEQ ID No: 22 and CDR3 comprising amino acid sequenceof SEQ ID No: 23,

CDR1 comprising amino acid sequence of SEQ ID No: 27, CDR2 comprisingamino acid sequence of SEQ ID No: 28 and CDR3 comprising amino acidsequence of SEQ ID No: 29,

CDR1 comprising amino acid sequence of SEQ ID No: 33, CDR2 comprisingamino acid sequence of SEQ ID No: 34 and CDR3 comprising amino acidsequence of SEQ ID No: 35, or

CDR1 comprising amino acid sequence of SEQ ID No: 39, CDR2 comprisingamino acid sequence of SEQ ID No: 40 and CDR3 comprising amino acidsequence of SEQ ID No: 41.

The amino acid sequences set forth in the above SEQ ID Nos. may be aminoacid sequences corresponding to the CDR1 to CDR3 of the heavy-chainvariable region.

In another example, the antibody or antigen-binding fragment of thepresent disclosure comprises:

CDR1 comprising amino acid sequence of SEQ ID No: 24, CDR2 comprisingamino acid sequence of SEQ ID No: 25 and CDR3 comprising amino acidsequence of SEQ ID No: 26,

CDR1 comprising amino acid sequence of SEQ ID No: 30, CDR2 comprisingamino acid sequence of SEQ ID No: 31 and CDR3 comprising amino acidsequence of SEQ ID No: 32,

CDR1 comprising amino acid sequence of SEQ ID No: 36, CDR2 comprisingamino acid sequence of SEQ ID No: 37 and CDR3 comprising amino acidsequence of SEQ ID No: 38, or

CDR1 comprising amino acid sequence of SEQ ID No: 42, CDR2 comprisingamino acid sequence of SEQ ID No: 43 and CDR3 comprising amino acidsequence of SEQ ID No: 44.

The amino acid sequences set forth in the above SEQ ID Nos. may be aminoacid sequences corresponding to the CDR1 to CDR3 of the light-chainvariable region.

Specifically, the antibody or antigen-binding fragment of the presentdisclosure comprises: one or more heavy chain variable region and lightchain variable region selected from the group consisting of:

heavy chain variable region comprising CDR1 comprising amino acidsequence of SEQ ID No: 21, CDR2 comprising amino acid sequence of SEQ IDNo: 22 and CDR3 comprising amino acid sequence of SEQ ID No: 23, andlight chain variable region comprising CDR1 comprising amino acidsequence of SEQ ID No: 24, CDR2 comprising amino acid sequence of SEQ IDNo: 25 and CDR3 comprising amino acid sequence of SEQ ID No: 26;

heavy chain variable region comprising CDR1 comprising amino acidsequence of SEQ ID No: 27, CDR2 comprising amino acid sequence of SEQ IDNo: 28 and CDR3 comprising amino acid sequence of SEQ ID No: 29, andlight chain variable region comprising CDR1 comprising amino acidsequence of SEQ ID No: 30, CDR2 comprising amino acid sequence of SEQ IDNo: 31 and CDR3 comprising amino acid sequence of SEQ ID No: 32;

heavy chain variable region comprising CDR1 comprising amino acidsequence of SEQ ID No: 33, CDR2 comprising amino acid sequence of SEQ IDNo: 34 and CDR3 comprising amino acid sequence of SEQ ID No: 35, andlight chain variable region comprising CDR1 comprising amino acidsequence of SEQ ID No: 36, CDR2 comprising amino acid sequence of SEQ IDNo: 37 and CDR3 comprising amino acid sequence of SEQ ID No: 38; and

heavy chain variable region comprising CDR1 comprising amino acidsequence of SEQ ID No: 39, CDR2 comprising amino acid sequence of SEQ IDNo: 40 and CDR3 comprising amino acid sequence of SEQ ID No: 41, andlight chain variable region comprising CDR1 comprising amino acidsequence of SEQ ID No: 42, CDR2 comprising amino acid sequence of SEQ IDNo: 43 and CDR3 comprising amino acid sequence of SEQ ID No: 44.

In one example, the antibody or antigen-binding fragment of the presentdisclosure comprises one or more heavy chain variable region and lightchain variable region comprising one or more amino acid sequenceselected from the group consisting of amino acid sequences of SEQ ID No:2, 4, 6, 8, 10, 12, 14, 16, 18 and 20.

Specifically, the antibody or antigen-binding fragment of the presentdisclosure comprises heavy chain variable region comprising amino acidsequence of SEQ ID No: 2, 4, 6, 8, or 10, and/or light chain variableregion comprising amino acid sequence of SEQ ID No: 12, 14, 16, 18 or20.

In detail, the antibody or antigen-binding fragment of the presentdisclosure comprises one or more heavy chain variable region and lightchain variable region selected from the group consisting of:

heavy chain variable region comprising amino acid sequence of SEQ ID No:2 and light chain variable region comprising amino acid sequence of SEQID No: 12;

heavy chain variable region comprising amino acid sequence of SEQ ID No:4 and light chain variable region comprising amino acid sequence of SEQID No: 14;

heavy chain variable region comprising amino acid sequence of SEQ ID No:6 and light chain variable region comprising amino acid sequence of SEQID No: 16;

heavy chain variable region comprising amino acid sequence of SEQ ID No:8 and light chain variable region comprising amino acid sequence of SEQID No: 18; and

heavy chain variable region comprising amino acid sequence of SEQ ID No:10 and light chain variable region comprising amino acid sequence of SEQID No: 20.

The present disclosure is directed to an isolated anti-FcRn antibody ora fragment thereof, which binds to an epitope of human FcRn comprisingresidues of S15, S16, P17, P19, G20, A23, F24, S40, L41, R42, R69, E72,K73, F75, L76, F79, G84 and Y88 of α chain extracellular domain (SEQ IDNO:45) and E36 from β2m chain (SEQ ID NO:46).

Further, the present disclosure is directed to an isolated anti-FcRnantibody or a fragment thereof, which binds to further one or moreresidue(s) selected from the group consisting of A13, V14, A18, T21,G43, K80, G83, K85 and G86 of α chain extracellular domain (SEQ IDNO:45).

“Fragment” or “antibody fragment” as the terms are used herein inreference to an antibody refer to a polypeptide derived from an antibodypolypeptide molecule (e.g., an antibody heavy or light chainpolypeptide) that does not comprise a full length antibody polypeptide,but which still comprises at least a portion of a full length antibodypolypeptide. Antibody fragments often comprise polypeptides thatcomprise a cleaved portion of a full length antibody polypeptide,although the term is not limited to such cleaved fragments. Since afragment, as the term is used herein in reference to an antibody,encompasses fragments that comprise single polypeptide chains derivedfrom antibody polypeptides (e.g. a heavy or light chain antibodypolypeptides), it will be understood that an antibody fragment may not,on its own, bind an antigen.

Fragments of the antibody according to the present disclosure include,but are not limited to, single-chain antibodies, bispecific,trispecific, and multispecific antibodies such as diabodies, triabodiesand tetrabodies, Fab fragments, F(ab′)₂ fragments, Fd, scFv, domainantibodies, dual-specific antibodies, minibodies, scap (sterolregulatory binding protein cleavage activating protein), chelatingrecombinant antibodies, tribodies or bibodies, intrabodies, nanobodies,small modular immunopharmaceuticals (SMIP), binding-domainimmunoglobulin fusion proteins, camelized antibodies, VHH containingantibodies, IgD antibodies, IgE antibodies, IgM antibodies, IgG1antibodies, IgG2 antibodies, IgG3 antibodies, IgG4 antibodies,derivatives in antibody constant regions, and synthetic antibodies basedon protein scaffolds, which have the ability to bind to FcRn. It will beobvious to those skilled in the art that any fragment of the antibodyaccording to the present disclosure will show the same properties asthose of the antibody of the present disclosure.

In addition, antibodies having a mutation in the variable region areincluded in the scope of the present disclosure. Examples of suchantibodies include antibodies having a conservative substitution of anamino acid residue in the variable region. As used herein, the term“conservative substitution” refers to substitution with another aminoacid residue having properties similar to those of the original aminoacid residue. For example, lysine, arginine and histidine have similarproperties in that they have a basic side-chain, and aspartic acid andglutamic acid have similar properties in that they have an acidic sidechain. In addition, glycine, aspargin, glutamine, serine, threonine,tyrosine, cysteine and tryptophan have similar properties in that theyhave an uncharged polar side-chain, and alanine, valine, leucine,threonine, isoleucine, proline, phenylalanine and methionine havesimilar properties in that they have a non-polar side-chain. Also,tyrosine, phenylalanine, tryptophan and histidine have similarproperties in that they have an aromatic side-chain. Thus, it will beobvious to those skilled in the art that, even when substitution ofamino acid residues in groups showing similar properties as describedabove occurs; it will show no particular change in the properties.Accordingly, antibodies having a mutation caused by conservativesubstitution in the variable region are included in the scope of thepresent disclosure.

In addition, the antibody according to the present disclosure or itsfragment may be used as a conjugate with another substance. Substancesthat may be used as conjugates with the antibody according to thepresent disclosure or its fragment include therapeutic agents that aregenerally used for the treatment of autoimmune diseases, substancescapable of inhibiting the activity of FcRn, and a moiety that isphysically associated with the antibody to improve its stabilizationand/or retention in circulation, for example, in blood, serum, lymph, orother tissues. For example, the FcRn-binding antibody can be associatedwith a polymer, e.g., a non-antigenic polymer such as polyalkylene oxideor polyethylene oxide. Suitable polymers will vary substantially byweight. Polymers having molecular number average weights ranging fromabout 200 to about 35,000 (or about 1,000 to about 15,000, and 2,000 toabout 12,500) can be used. For example, the FcRn-binding antibody can beconjugated to water soluble polymers, e.g., hydrophilic polyvinylpolymers, e.g. polyvinylalcohol and polyvinylpyrrolidone. A non-limitinglist of such polymers includes, but is not limited to, polyalkyleneoxide homopolymers such as polyethylene glycol (PEG) or polypropyleneglycols, polyoxyethylenated polyols, copolymers thereof and blockcopolymers thereof, provided that the water solubility of the blockcopolymers is maintained.

In another embodiment, the present disclosure is directed to apharmaceutical composition for treating autoimmune disease comprisingthe anti-FcRn antibody, and one or more pharmaceutically acceptablecarriers. Also, the present disclosure is directed to a method oftreating autoimmune disease comprising administering an effective amountof antibody binding specifically to FcRn to a patient in need thereof.

The pharmaceutical composition may comprise a pharmaceuticallyacceptable carrier, excipient, and the like, which are well known in theart. The pharmaceutically acceptable carriers should be compatible withthe active ingredient such as the antibody or a fragment thereofaccording to the present disclosure and may be physiological saline,sterile water, Ringer's solution, buffered saline, dextrose solution,maltodextrin solution, glycerol, ethanol, or a mixture of two or morethereof. In addition, the pharmaceutical composition of the presentdisclosure may, if necessary, comprise other conventional additives,including antioxidants, buffers, and bacteriostatic agents. Further, thepharmaceutical composition of the present disclosure may be formulatedas injectable forms such as aqueous solutions, suspensions or emulsionswith the aid of diluents, dispersants, surfactants, binders andlubricants. In addition, the pharmaceutical composition of the presentdisclosure may be provided by formulating into a various form such aspowder, tablet, capsule, liquid, inject, ointment, syrup etc, andsingle-dosage or multi-dosage container such as sealed ample or vial.

The pharmaceutical composition of the present disclosure may be appliedto all autoimmune diseases that are mediated by IgG and FcRn, andtypical examples of such autoimmune diseases include, but are notlimited to, immune neutropenia, Guillain-Barré syndrome, epilepsy,autoimmune encephalitis, Isaac's syndrome, nevus syndrome, pemphigusvulgaris, Pemphigus foliaceus, Bullous pemphigoid, epidermolysis bullosaacquisita, pemphigoid gestationis, mucous membrane pemphigoid,antiphospholipid syndrome, autoimmune anemia, autoimmune Grave'sdisease, Goodpasture's syndrome, myasthenia gravis, multiple sclerosis,rheumatoid arthritis, lupus, idiopathic thrombocytopenic purpura, lupusnephritis and membranous nephropathy.

In the treatment method according to the present disclosure, the dose ofthe antibody can be suitably determined by taking into consideration thepatient's severity, condition, age, case history and the like. Forexample, the antibody may be administered at a dose of 1 mg/kg to 2g/kg. The antibody may be administered once or several times.

The present disclosure also provides a method for ameliorating anautoimmune or alloimmune condition, including administering the antibodyof the present disclosure or a fragment of the antibody to a subject inneed of treatment. The present disclosure also provides a specificanti-FcRn therapy.

The inventive method for ameliorating an autoimmune or alloimmunecondition or the inventive anti-FcRn therapy can be achieved byadministering the pharmaceutical composition of the present disclosureto a subject. The pharmaceutical composition of the present disclosurecan be administered orally or parenterally. The pharmaceuticalcomposition according to the present disclosure can be administered byvarious routes, including, but not limited to, oral, intravenous,intramuscular, intra-arterial, intramedullary, intradural, intracardial,transdermal, subcutaneous, intraperitoneal, gastrointestinal,sublingual, and local routes. The dose of the composition of the presentdisclosure may vary depending on various factors, such as a patient'sbody weight, age, sex, health condition and diet, the time and method ofadministration, excretion rate, and severity of a disease, and may beeasily determined by a person of ordinary skill in the art. Generally,1-200 mg/kg, and preferably, 1-40 mg/kg of the composition may beadministered to patients afflicted with autoimmune or alloimmuneconditions, and these regimens are preferably designed to reduce theserum endogenous IgG concentration to less than 75% of pretreatmentvalues. Intermittent and/or chronic (continuous) dosing strategies maybe applied in view of the conditions of patients.

In another embodiment, the present disclosure also provides a diagnosticcomposition comprising the antibody of the present disclosure or afragment thereof, and a diagnostic method that uses the diagnosticcomposition. In other words, the antibody of the present disclosure or afragment thereof, which binds to FcRn, has in vitro and in vivodiagnostic utilities.

In another embodiment, the present disclosure is directed to acomposition for detecting FcRn comprising the anti-FcRn antibody or afragment thereof. The present disclosure also provides a method, systemor device for detecting FcRn in vivo or in vitro comprising treating theanti-FcRn antibody.

The in vitro detection method, system or device might, for example,include (1) bringing a sample into contact with the FcRn-bindingantibody; (2) detecting the formation of a complex between theFcRn-binding antibody and the sample; and/or (3) bringing a referencesample (e.g., a control sample) into contact with the antibody; and (4)determining the degree of formation of the complex between the antibodyand the sample by comparison with that in the reference sample. A change(e.g., a statistically significant change) in the formation of thecomplex in the sample or the subject as compared to that in the controlsample or subject indicates the presence of FcRn in the sample.

The in vivo detection method, system or device may include: (1)administering the FcRn-binding antibody to a subject; and (2) detectingthe formation of a complex between the FcRn-binding antibody and thesubject. The detecting may include determining location or time offormation of the complex. The FcRn-binding antibody can be directly orindirectly labeled with a detectable substance to facilitate detectionof the bound or unbound antibody. Suitable detectable substances includevarious enzymes, prosthetic groups, fluorescent materials, luminescentmaterials, and radioactive materials. The formation of a complex betweenthe FcRn-binding antibody and FcRn can be detected by measuring orvisualizing the antibody bound or not bound to FcRn. A conventionaldetection assay, for example, enzyme-linked immunosorbent assay (ELISA),radioimmunoassay (RIA) or tissue immunohistochemistry may be used. Inaddition to labeling of the FcRn-binding antibody, the presence of FcRncan be assayed in a sample by competition immunoassay using a standardlabeled with a detectable substance and an unlabeled FcRn-bindingantibody. In one example of this assay, the biological sample, thelabeled standard and the FcRn-binding antibody are combined and theamount of labeled standard unbound to FcRn is determined. The amount ofFcRn in the biological sample is inversely proportional to the amount oflabeled standard unbound to FcRn.

For detection purposes, the antibody of the present disclosure or afragment thereof can be labeled with a fluorophore and a chromophore.Because antibodies and other proteins absorb light having wavelengths upto about 310 nm, the fluorescent moieties should be selected to havesubstantial absorption at wavelengths above 310 nm and preferably above400 nm. The antibody of the present disclosure or a fragment thereof canbe labeled with a variety of suitable fluorescers and chromophores. Onegroup of fluorescers is xanthene dyes, which include fluoresceins andrhodamines. Another group of fluorescent compounds are naphthylamines.Once labeled with a fluorophore or chromophore, the antibody can be usedto detect the presence or localization of the FcRn in a sample, e.g.,using fluorescent microscopy (such as confocal or deconvolutionmicroscopy).

Detection of the presence or localization of FcRn using the antibody ofthe present disclosure or a fragment thereof can be performed by variousmethods such as histological analysis, protein arrays and FACS(Fluorescence Activated Cell Sorting).

In the present disclosure, the presence of FcRn or FcRn-expressingtissue in vivo can be performed by an in vivo Imaging method. The methodincludes (i) administering to a subject (e.g., a patient having anautoimmune disorder) an anti-FcRn antibody, conjugated to a detectablemarker; and (ii) exposing the subject to a means for detecting saiddetectable marker to the FcRn-expressing tissues or cells. For example,the subject is imaged, e.g., by NMR or other tomographic means. Examplesof labels useful for diagnostic imaging include radiolabels, fluorescentlabels, positron emitting isotopes, chemiluminescers, and enzymaticmarkers. A radiolabeled antibody can also be used for in vitrodiagnostic tests. The specific activity of a isotopically-labeledantibody depends upon the half life, the isotopic purity of theradioactive label, and how the label is incorporated into the antibody.

The present disclosure also provides a kit comprising an antibody thatbinds to FcRn a fragment thereof and instructions for diagnostic use,e.g., the use of the FcRn-binding antibody or a fragment thereof, todetect FcRn, in vitro, e.g., in a sample, e.g., a biopsy or cells from apatient having an autoimmune disorder, or in vivo, e.g., by imaging asubject. The kit can further contain at least one additional reagent,such as a label or additional diagnostic agent. For in vivo use, theantibody can be formulated as a pharmaceutical composition.

In another embodiment, the present disclosure is directed topolynucleotide sequences that encode the antibody of the presentdisclosure or a fragment thereof.

In an example, a polynucleotide sequence that encodes the antibody ofthe present disclosure or a fragment thereof is a sequence, which has atleast 90% homology with one or more sequence selected from the groupconsisting of SEQ ID No: 1, 3, 5, 7, 9, 11, 13, 15, 17 and 19 orsequence having a homology of more than 90%, when compared with thesequences mentioned above.

Specifically, a polynucleotide sequence of the antibody of the presentdisclosure or a fragment thereof is a sequence that encodes heavy chainof the antibody of the present disclosure is SEQ ID No: 1, 3, 5, 7 or 9,and/or a sequence that encodes light chain of the antibody of thepresent disclosure is SEQ ID No: 11, 13, 15, 17 or 19.

In another embodiment, the present disclosure is directed to arecombinant expression vector comprising the polynucleotide, host cell,which is transected with the recombinant expression vector and method ofpreparing an antibody binding specifically to FcRn or a fragment thereofby using the recombinant expression vector and host cell.

In one embodiment, the antibody or a fragment thereof according to thepresent disclosure is preferably produced by expression and purificationusing a gene recombination method. Specifically, the variable regionsthat encode the inventive antibody that binds specifically to FcRn areproduced by being expressed in separate host cells or simultaneously ina single host cell.

As used herein, the term “recombinant vector” refers to an expressionvector capable of expressing the protein of interest in a suitable hostcell and means a DNA construct including essential regulatory elementsoperably linked to express a nucleic acid insert. As used herein, theterm “operably linked” means that a nucleic acid expression controlsequence is functionally linked to a nucleic acid sequence encoding theprotein of interest so as to execute general functions. Operable linkagewith the recombinant vector can be performed using a gene recombinationtechnique well known in the art, and site-specific DNA cleavage andligation can be easily performed using enzymes generally known in theart.

A suitable expression vector that may be used in the present disclosuremay include expression regulatory elements such as a promoter, anoperator, an initiation codon, a stop codon, a polyadenylation signal,and an enhancer, as well as a signal sequence for membrane targeting orsecretion. The initiation and stop codons are generally considered aspart of a nucleotide sequence encoding the immunogenic target protein,and are necessary to be functional in an individual to whom a geneticconstruct has been administered, and must be in frame with the codingsequence. Promoters may generally be constitutive or inducible.Prokaryotic promoters include, but are not limited to, lac, tac, T3 andT7 promoters. Eukaryotic promoters include, but are not limited to,simian virus 40 (SV40) promoter, mouse mammary tumor virus (MMTV)promoter, human immunodeficiency virus (HIV) promoter such as the HIVLong Terminal Repeat (LTR) promoter, moloney virus promoter,cytomegalovirus (CMV) promoter, epstein barr virus (EBV) promoter, roussarcoma virus (RSV) promoter, as well as promoters from human genes suchas human β-actin, human hemoglobin, human muscle creatine and humanmetallothionein. The expression vector may include a selectable markerthat allows selection of host cells containing the vector. Genes codingfor products that confer selectable phenotypes, such as resistance todrugs, nutrient requirement, resistance to cytotoxic agents orexpression of surface proteins, are used as general selectable markers.Since only cells expressing a selectable marker survive in theenvironment treated with a selective agent, transformed cells can beselected. Also, a replicable expression vector may include a replicationorigin, a specific nucleic acid sequence that initiates replication.Recombinant expression vectors that may be used in the presentdisclosure include various vectors such as plasmids, viruses andcosmids. The kind of recombinant vector is not specifically limited andthe recombinant vector could function to express a desired gene andproduce a desired protein in various host cells such as prokaryotic andeukaryotic cells. However, it is preferred to use a vector that canproduce a large amount of a foreign protein similar to a natural proteinwhile having strong expression ability with a promoter showing strongactivity.

In the present disclosure, a variety of expression host/vectorcombinations may be used to express the antibody or a fragment thereofaccording to the present disclosure. For example, expression vectorssuitable for the eukaryotic host include, but are not limited to, SV40,bovine papillomavirus, adenovirus, adeno-associated virus,cytomegalovirus, and retrovirus. Expression vectors that may be used forbacterial hosts include bacterial plasmids such as pET, pRSET,pBluescript, pGEX2T, pUC, col E1, pCR1, pBR322, pMB9 and derivativesthereof, a plasmid such as RP4 having a wider host range, phage DNArepresented as various phage lambda derivatives such as gt10, gt11 andNM989, and other DNA phages such as M13 and filamentous single-strandedDNA phage. Expression vectors useful in yeast cells include 2 μm plasmidand derivatives thereof. A vector useful in insect cells is pVL941.

The recombinant vector is introduced into a host cell to form atransformant. Host cells suitable for use in the present disclosureinclude prokaryotic cells such as E. coli, Bacillus subtilis,Streptomyces sp., Pseudomonas sp., Proteus mirabilis and Staphylococcussp., fungi such as Aspergillus sp., yeasts such as Pichia pastoris,Saccharomyces cerevisiae, Schizosaccharomyces sp., and Neurosporacrassa, and eukaryotic cells such as lower eukaryotic cells, and higherother eukaryotic cells such as insect cells.

Host cells that may be used in the present disclosure are preferablyderived from plants and mammals, and examples thereof include, but arenot limited to, monkey kidney cells (COS7), NSO cells, SP2/0, Chinesehamster ovary (CHO) cells, W138, baby hamster kidney (BHK) cells, MDCK,myeloma cells, HuT 78 cells and HEK293 cells. Preferably, CHO cells areused.

In the present disclosure, transfection or transformation into a hostcell includes any method by which nucleic acids can be introduced intoorganisms, cells, tissues or organs, and, as known in the art, may beperformed using a suitable standard technique selected according to thekind of host cell. These methods include, but are not limited to,electroporation, protoplast fusion, calcium phosphate (CaPO₄)precipitation, calcium chloride (CaCl₂) precipitation, agitation withsilicon carbide fiber, and agrobacterium-, PEG-, dextran sulfate-,lipofectamine- and desiccation/inhibition-mediated transformation.

The FcRn-specific antibody or a fragment thereof according to thepresent disclosure can be produced in large amounts by culturing thetransformant comprising the recombinant vector in nutrient medium, andthe medium and culture conditions that are used in the presentdisclosure can be suitable selected depending on the kind of host cell.During culture, conditions, including temperature, the pH of medium, andculture time, can be controlled so as to be suitable for the growth ofcells and the mass production of protein. The antibody or antibodyfragment produced by the recombination method as described can becollected from the medium or cell lysate and can be isolated andpurified by conventional biochemical isolation techniques (Sambrook etal., Molecular Cloning: A laboratory Manual, 2nd Ed., Cold Spring HarborLaboratory Press (1989); Deuscher, M., Guide to Protein PurificationMethods Enzymology, Vol. 182. Academic Press. Inc., San Diego, Calif.(1990)). These techniques include, but are not limited to,electrophoresis, centrifugation, gel filtration, precipitation,dialysis, chromatography (ion exchange chromatography, affinitychromatography, immunosorbent chromatography, size exclusionchromatograophy, etc.), isoelectric point focusing, and variousmodifications and combinations thereof. Preferably, the antibody or theantibody fragment is isolated and purified using protein A.

The antibodies of the present disclosure showed antigen bindingabilities (KD values) from about 300 pM or less to about 2 nM or less atpH 7.4, and also showed KD values from 2 nM or less to 900 pM or less atpH 6.0. The antibodies of the present disclosure have a strong hFcRnbinding affinity of 0.01-2 nM and thus it is believed that theantibodies bound to the outside of cells maintain even their binding toendosomes, suggesting that these antibodies have an excellent effect ofblocking the binding of autoantibodies to hFcRn. In addition, thiseffect of blocking the binding of autoantibodies to hFcRn was alsoconfirmed in a blocking assay performed using human FcRn-expressingcells and FACS.

EXAMPLES

Hereinafter, the present disclosure will be described in further detailwith reference to examples. It will be obvious to a person havingordinary skill in the art that these examples are illustrative purposesonly and are not to be construed to limit the scope of the presentdisclosure.

Example 1: Construction of Anti-FcRn-Expressing Library Using TransgenicRats

Immunization was performed using a total of six transgenic rats(OmniRat®, OMT). As an immunogen, human FcRn was used. Both footpads ofthe rats were immunized eight times with 0.0075 mg of human FcRn (eachtime) together with an adjuvant at 3-day intervals for 24 days. On day28, the rats were immunized with 5-10 μg of the immunogen diluted in PBSbuffer. On day 28, rat serum was collected and used to measure theantibody titer. On day 31, the rats were euthanized, and the popliteallymph node and the inguinal lymph node were recovered for fusion withP3X63/AG8.653 myeloma cells.

ELISA analysis was performed to measure the antibody titer in rat serum.Specifically, human FcRn was diluted in PBS (pH 6.0 or pH 7.4) buffer tomake 2 μg/mL of a solution, and 100 μl of the solution was coated oneach well of a 96-well plate, and then incubated at 4° C. for at least18 hours. Each well was washed three times with 300 μL of washing buffer(0.05% Tween 20 in PBS) to remove unbound human FcRn, and then 200 μL ofblocking buffer was added to each well and incubated at room temperaturefor 2 hours. A test serum sample was diluted at 1/100, and then thesolution was serially 2-fold diluted to make a total of 10 test sampleshaving a dilution factor of 1/100 to 1/256,000). After blocking, eachwell was washed with 300 μL of washing buffer, and then each test samplewas added to each cell and incubated at room temperature for 2 hours.After washing three times, 100 μL of a 1:50,000 dilution of secondarydetection antibody in PBS buffer was added to each well and incubated atroom temperature for 2 hours. After washing three times again, 100 μL ofTMB solution was added to each well and allowed to react at roomtemperature for 10 minutes, and then 50 μL of 1M sulfuricacid-containing stop solution was added to each well to stop thereaction, after which the OD value at 450 nm was measured with amicroplate reader. Regarding the anti-hFcRn IgG titer resulting fromimmunization was higher than that in the pre-immune serum of the rats,which was not immunized with the OD value at 450 nm in the 1/100dilution condition 1.0 or higher, suggesting that the rats were wellimmunized.

A total of three hybridoma libraries A, B and C fused using polyethyleneglycol were made. Specifically, transgenic rats 1 and 5 were used tomake hybridoma library A, and rats 2 and 6 were used to make hybridomalibrary B, and rats 3 and 4 were used to make hybridoma library C. Ahybridoma library fusion mixture for constructing each hybridoma librarywas cultured in HAT-containing medium for 7 days so that only cellsfused to HAT would be selected. Hybridoma cells viable in the HAT mediumwere collected and cultured in HT media for about 6 days, and then thesupernatant was collected, and the amount of rat IgG in the supernatantwas measured using a rat IgG ELISA kit (RD-biotech). Specifically, eachsample was diluted at 1:100, and 100 μL of the dilution was added toeach well of an ELISA plate and mixed with peroxidase-conjugatedanti-rat IgG, followed by reaction at room temperature for 15 minutes.100 μL of TMB solution was added to each well and allowed to react atroom temperature for 10 minutes, and then 50 μL of 1M sulfuricacid-containing stop solution was added to each well to stop thereaction. Next, the OD value at 450 nm was measured with a microplatereader.

Example 2: Evaluation of the Antigen Binding Affinity and IgG BindingBlocking Ability of Anti-hFcRn Antibodies of Hybridoma Libraries

To analyze the binding of antibodies to human FcRn, the same ELISAanalysis (pH 6.0 and pH 7.4) as mentioned above was performed. Theresults of evaluation of the hFcRn binding of the three hybridomalibraries A, B and C indicates that the hFcRn binding affinity washigher in the order of A>C>B at both pH 6.0 and pH 7.4.

Using the culture supernatants of the three hybridoma libraries, theevaluation of the hFcRn binding affinity by FACS at 5 ng/mL and 25 ng/mLwas performed at pH 6.0 and pH 7.4. Human FcRn-stable expressing HEK293cells were detached from a flask, and then suspended in reaction buffer(0.05% BSA in PBS, pH 6.0 or pH 7.4). The suspension was diluted to acell density of 2×10⁶ cells/mL, and 50 μL of the dilution was added toeach well of a 96-well plate. Then, 50 μL of the hybridoma libraryculture supernatant diluted to each of 10 ng/mL and 50 ng/mL was addedto each well and suspended to allow antibody to bind. A488 rabbitanti-IgG goat antibody was diluted at 1:200 in reaction buffer, and 100μL of the dilution was added to each well and mixed with the cellpellets to perform a binding reaction, and then 150 μL of reactionbuffer was added to each well. Measurement was performed in FACS (BD).Like the ELISA results, it could be seen that hybridoma library A showedthe highest binding affinity.

Evaluation of the human FcRn blocking ability of the hybridoma libraryby FACS was performed at pH 6.0. Specifically, naïve HEK293 cells andhuman FcRn-overexpressing HEK293 cells were suspended in reaction buffer(0.05% BSA in PBS, pH 6.0). 1×10⁵ cells were added to a 96-well plate,and treated with each of 4 nM of each hybridoma library culturesupernatant and 0.4 nM of a 10-fold dilution of the supernatant. Toconfirm the hIgG blocking ability, 100 nM A488-hIgG1 was added to eachwell, and then incubated on ice for 90 minutes. After completion of thereaction, the cell pellets were washed with 100 μL of reaction buffer,and transferred into a U-shaped round bottom tube, followed bymeasurement in FACS. The amount of 100 nM A488-hIgG1 remaining in thehuman FcRn-overexpressing stable cells was measured, and then theblocking (%) was calculated. As an isotype control, hIgG1 was used, andas a positive control, previously developed HL161-1Ag antibody was usedto comparatively evaluate the antibody blocking effect. Each control wasanalyzed at concentrations of 1 μM and 2 μM, and the hybridoma librarysample was measured at two concentrations of 0.4 nM and 4 nM. As aresult, it was found that hybridoma library A showed the highestblocking effect.

Example 3: Isolation of Hybridoma Clone by FACS and Selection of HumanAntibodies

Using hybridoma library A showing the highest human FcRn bindingaffinity and blocking effect, clones were isolated by FACS (flowcytometry) to thereby obtain a total of 442 single clones. The isolatedmonoclones were cultured in HT media, and the supernatant was collected.Antibody-expressing hybridoma clones binding to hFcRn in the supernatantwere selected by FACS. As a result, it could be seen that 100 clones(M1-M100) did strongly bind to the hFcRn-expressing HEK293 cells.

RNA was isolated from the 100 monoclones selected by FACS analysis andthe isolated RNA was sequenced. In the first-step sequencing, 88 of the100 monoclones were sequenced, and divided according to the amino acidsequence into a total of 35 groups (G1 to G38). The culture supernatantsof the representative clones of 33 groups excluding two clones (G33 andG35) whose media were not available were diluted at a concentration of100 ng/mL, and the binding affinity for hFcRn was evaluated by ELISA.

In the same manner as described above, evaluation of the hFcRn bindingaffinity by FACS was performed at pH 6.0 and 7.4. The order of thebinding affinity of the clones was similar between the pHs, and thebinding intensity appeared at various levels.

In addition, evaluation of the hFcRn blocking effects of the 33 cloneswas performed by FACS at pH 6.0. The blocking (%) was calculated basedon the measured MFI value. Based on the results of analysis of theblocking % at a concentration of 1667 pM, the clones were divided into atotal of the following four groups: group A: 70-100%; group B: 30-70%;group C: 10-30%; and group D: 10% or less.

For kinetic analysis of the hybridoma clones by SPR, human FcRn wasimmobilized, and then the analysis was performed using the hybridomaculture as an analyte. Most of the clones excluding several clonesshowed a k_(on) of 10⁶ M or higher and a k_(off) value of 10⁻³ M orlower. In conclusion, it was shown that all the clones had a KD value of10⁻⁹ to 10⁻¹¹ M.

Among the five hybridoma clones, the genes of 18 clones having noN-glycosylation site or free cysteine in the CDR sequences of groups Aand B divided according to the results of analysis of the hFcRn blockingeffect were converted to whole human IgG sequences.

Specifically, the amino acid sequence similarity between the VH and VLof the 18 selected antibodies and the human germ line antibody group wasexamined using the Ig BLAST program of the NCBI webpage.

In order to clone the 18 human antibody genes, restriction enzymerecognition sites were inserted into both ends of the genes in thefollowing manner. EcoRI/ApaI were inserted into the heavy-chain variabledomain (VH); EcoRI/XhoI were inserted into the light-chain lambdavariable domain (VL(λ)); EcoRI/NheI restriction enzyme recognitionssites were inserted into the light-chain kappa variable domain (VL(κ)).In the case of the light-chain variable domain, the light-chain lambdavariable (VL(λ)) gene sequence was linked to the human light-chainconstant (LC(λ) region gene during gene cloning, and the light-chainkappa variable (VL(κ)) gene sequence was linked to the human light-chainconstant (LC(κ) region gene.

In cloning into pCHO1.0 expression vectors for expression of antibodiesin animal cells, the light-chain and heavy-chain genes were insertedafter cleavage with EcoRV, PacI, AvrII and BstZ17I restriction enzymes.In order to examine whether pCHO1.0 expression vectors containing the 18selected human antibody genes were consistent with the synthesized genesequences, DNA sequencing was performed.

Using the pCHO1.0 expression vectors that are animal cell expressionsystems containing all the antibody light-chain and heavy-chain genes,whole human IgG was expressed. The human antibody was obtained bytransiently transfecting the plasmid DNA of each of the antibodies intoCHO-S cells and purifying the antibody, secreted into the medium, byprotein A column.

Human IgG was injected into hFcRn-expressing Tg32 (hFcRn+/+, hJβ2m+/+,mFcRn−/−, mβ2m−/−) mice (Jackson Laboratory), and then the 18 humanantibodies converted to the human IgG sequences were administered to themice in order to examine whether the antibodies would influence thecatabolism of human IgG.

Based on the in vitro analysis results for binding affinity (KD) for theantigen and the analysis of human FcRn binding affinity and blockingeffect by FACS, and the in vivo analysis of catabolism of human IgG,four human anti-FcRn antibody proteins (HL161A, HL161B, HL161C andHL161D) that most effectively acted were selected (FIG. 1). In addition,an HL161BK antibody having no N-glycosylation site was prepared bysubstituting asparagine (N) at position 83 of the heavy-chain variableframework of the HL161B antibody with lysine (K). The nucleotidesequences, amino acid sequences and CDR sequences of the light-chain andheavy-chain variable regions of each antibody are shown in Tables 1, 2and 3.

TABLE 1Polynucleotide sequences of heavy-chain and light-chain variable domains of selected human FcRn antibodies Heavy-chain Light-chainvariable domain sequence variable domain sequence SEQ SEQ Antibody ID IDname NO. Polynucleotide sequence NO. Polynucleotide sequence HL161A 1GAAGTGCAGC TGCTGGAATC 11 TCTTACGTGC TGACCCAGCC CGGCGGAGGC CTGGTGCAGCCCCCTCCGTG TCTGTGGCTC CTGGCGGCTC TCTGAGACTG CTGGCCAGAC CGCCAGAATCTCCTGCGCCG CCTCCGAGTT ACCTGTGGCG GCAACAACAT CACCTTCGGC AGCTGCGTGACGGCTCCACC TCCGTGCACT TGACCTGGGT CCGACAGGCT GGTATCAGCA GAAGCCCGGCCCCGGCAAGG GCCTGGAATG CAGGCCCCCG TGCTGGTGGT GGTGTCCGTG ATCTCCGGCTGCACGACGAC TCCGACCGGC CCGGCGGCTC CACCTACTAC CTTCTGGCAT CCCTGAGCGGGCCGACTCTG TGAAGGGCCG TTCTCCGGCT CCAACTCCGG GTTCACCATC TCCCGGGACACAACACCGCC ACCCTGACCA ACTCCAAGAA CACCCTGTAC TCTCCAGAGT GGAAGCCGGCCTGCAGATGA ACTCCCTGCG GACGAGGCCG ACTACTACTG GGCCGAGGAC ACCGCCGTGTCCAAGTGCGA GACTCCTCCT ACTACTGCGC CAAGACCCCC CCGACCACGT GATCTTCGGCTGGTGGCTGC GGTCCCCCTT GGAGGCACCA AGCTGACCGT CTTCGATTAC TGGGGCCAGGGCTGGGCCAG CCTAAGGCCG GCACCCTGGT GACAGTGTCC CTCCCTCCGT GACCCTG TCCHL161B 3 CAACTGTTGC TCCAGGAATC 13 TCTTACGTGC TGACCCAGTCCGGTCCTGGT CTTGTAAAGC CCCCTCCGTG TCCGTGGCTC CATCTGAGAC TCTCTCCCTTCTGGCCAGAC CGCCAGAATC ACCTGTACCG TTAGCGGAGG ACCTGTGGCG GCAACAACATAAGTCTTTCC TCAAGCTTCT CGGCTCCAAG TCCGTGCACT CCTACTGGGT GTGGATCAGAGGTATCAGCA GAAGCCCGGC CAGCCTCCCG GAAAAGGGTT CAGGCCCCCG TGCTGGTGGTGGAGTGGATT GGCACAATAT GTACGACGAC TCCGACCGGC ACTACTCCGG CAACACTTACCCTCTGGCAT CCCTGAGCGG TATAACCCCA GCCTGAAGAG TTCTCCGCCT CCAACTCCGGCAGGCTGACT ATCTCTGTCG CAACACCGCC ACCCTGACCA ACACCAGTAA AAATCACTTTTCTCCAGAGT GGAAGCCGGC TCTCTGAATC TGTCTTCAGT GACGAGGCCG ACTACTACTGGACCGCAGCC GACACCGCCG CCAAGTGTGG GACTCCTCCT TGTATTATTG CGCTCGGCGCCCGACCACGT GGTGTTCGGC GCCGGGATTC TGACAGGCTA GGAGGCACCA AGCTGACCGTTCTGGATTCA TGGGGCCAGG GCTGGGCCAG CCTAAGGCCG GGACATTGGT TACAGTGTCTCTCCCTCCGT GACCCTG AGT HL161BK 5 CAGCTGCTGC TGCAAGAATC 15TCTTACGTGC TGACCCAGTC CGGCCCTGGC CTGGTGAAAC CCCCTCCGTG TCCGTGGCTCCCTCCGAGAC ACTGTCCCTG CTGGCCAGAC CGCCAGAATC ACCTGCACCG TGTCCGGCGGACCTGTGGCG GCAACAACAT CTCCCTGTCC TCCAGCTTCT CGGCTCCAAG TCCGTGCACTCCTACTGGGT CTGGATCCGG GGTATCAGCA GAAGCCCGGC CAGCCCCCTG GCAAGGGCCTCAGGCCCCCG TGCTGGTGGT GGAATGGATC GGCACCATCT GTACGACGAC TCCGACCGGCACTACTCCGG CAACACCTAC CCTCTGGCAT CCCTGAGCGG TACAACCCCA GCCTGAAGTCTTCTCCGCCT CCAACTCCGG CCGGCTGACC ATCTCCGTGG CAACACCGCC ACCCTGACCAACACCTCCAA GAACCACTTC TCTCCAGAGT GGAAGCCGGC AGCCTGAAGC TGTCCTCCGTGACGAGGCCG ACTACTACTG GACCGCCGCT GACACCGCCG CCAAGTGTGG GACTCCTCCTTGTACTACTG TGCCAGAAGG CCGACCACGT GGTGTTCGGC GCCGGCATCC TGACCGGCTAGGAGGCACCA AGCTGACCGT CCTGGACTCT TGGGGCCAGG GCTGGGCCAG CCTAAGGCCGGCACCCTGGT GACAGTGTCC CTCCCTCCGT GACCCTG TCC HL161C 7CAGGTGCAGC TCGTGCAGTC 17 GACATCCAGA TGACCCAGTC CGGCGCAGAG GTCAAAAAGCACCATCATCC CTTTCCGCAT CTGGTGCATC TGTGAAAGTG CTGTCGGAGA TAGAGTGACTAGTTGCAAGG CTAGCGGCTA ATCACCTGCA GGGCTTCTCA CACCTTTACC GGATGTTATAAGGTATTTCC AACTACCTCG TGCATTGGGT ACGCCAAGCC CCTGGTTCCA GCAAAAGCCACCCGGACAAG GCTTGGAATG GGTAAAGCCC CAAAGAGCTT GATGGGGCGT ATCAACCCAAGATCTACGCC GCTTCTAGTC ACTCTGGCGG GACTAATTAC TGCAGAGTGG AGTTCCTAGTGCCCAGAAGT TTCAGGGAAG AAGTTCTCCG GCTCTGGCAG GGTGACTATG ACAAGGGACATGGCACAGAT TTTACCTTGA CATCCATATC CACCGCTTAT CCATTTCCAG CCTGCAGTCTATGGACCTGT CTCGACTGCG GAGGATTTCG CTACCTACTA GTCTGATGAT ACAGCCGTTTTTGTCAGCAG TATGACAGCT ATTACTGCGC CAGAGACTAC ATCCCCCCAC ATTTGGGGGGAGCGGATGGA GCTTCGATTA GGCACTAAGG TGGAGATAAA TTGGGGGCAG GGTACTTTGGACGGACAGTG GCTGCCCCTT TCACAGTTTC AAGT CTGTCTTTAT T HL161D 9CAGCTGCAGT TGCAGGAGTC 19 AGCTATGAGC TGACCCAGCC AGGCCCCGGT TTGGTTAAGCTCTGAGCGTA TCTGTCGCTC CTTCTGAAAC CCTTTCTCTC TCGGCCAGAC AGCCAGAATTACATGCACAG TATCCGGTGG ACCTGTGGCG GCAATAACAT CTCCATCTCC AGTTCAAGTTAGGATCCAAA AATGTTCACT ACTACTGGGG ATGGATCCGG GGTATCAGCA AAAACCTGGCCAACCCCCAG GAAAAGGGCT CAAGCTCCCG TGCTCGTGAT GGAGTGGATT GGCAATATATCTACCGGGAC TCTAACCGAC ATTACTCTGG GTCCACCTAT CCAGTGGAAT CCCCGAACGCTACAACCCTT CCCTGATGAG TTTAGCGGTT CCAACTCTGG TAGAGTGACC ATCAGCGTGGAAATACAGCT ACTCTGACTA ACACAAGCAA AAACCAATTC TCTCCAGGGC TCAGGCCGGGAGCCTGAAGC TTTCTAGCGT GATGAGGCCG ATTACTACTG GACCGCTGCC GACACAGCTGCCAGGTGTGG GACTCAAGCA TCTATTACTG TGCCCGCCAG CAGTGGTCTT CGGCGGAGGTCTTAGTTATA ACTGGAATGA ACCAAGTTGA CTGTTCTTGG TAGGCTGTTT GATTACTGGGGCAGCCAAAG GCCGCACCTT GCCAGGGGAC TCTCGTTACA CAGTGACCCT G GTCAGCAGC

TABLE 2 Amino acid sequences of heavy-chain and light-chain variabledomains of selected human FcRn antibodies Heavy-chain Light-chainvariable domain sequence variable domain sequence SEQ SEQ Antibody ID IDname NO. Polynucleotide sequence NO. Polynucleotide sequence HL161A  2EVQLLESGGG LVQPGGSLRL 12 SYVLTQPPSV SVAPGQTARI SCAASEFTFG SCVMTWVRQATCGGNNIGST SVHWYQQKPG PGKGLEWVSV ISGSGGSTYY QAPVLVVHDD SDRPSGIPERADSVKGRFTI SRDNSKNTLY FSGSNSGNTA TLTISRVEAG LQMNSLRAED TAVYYCAKTPDEADYYCQVR DSSSDHVIFG WWLRSPFFDY WGQGTLVTVSS GGTKLTVLGQ PKAAPSVTL HL161B 4 QLLLQESGPG LVKPSETLSL 14 SYVLTQSPSV SVAPGQTARI TCTVSGGSLS SSFSYWVWIRTCGGNNIGSK SVHWYQQKPG QPPGKGLEWI GTIYYSGNTY QAPVLVVYDD SDRPSGIPERYNPSLKSRLT ISVDTSKNHF FSASNSGNTA TLTISRVEAG SLNLSSVTAA DTAVYYCARRDEADYYCQVW DSSSDHVVFG AGILTGYLDS WGQGTLVTVSS GGTKLTVLGQ PKAAPSVTLHL161BK  6 QLLLQESGPG LVKPSETLSL 16 SYVLTQSPSV SVAPGQTARITCTVSGGSLS SSFSYWVWIR TCGGNNIGSK SVHWYQQKPG QPPGKGLEWI GTIYYSGNTYQAPVLVVYDD SDRPSGIPER YNPSLKSRLT ISVDTSKNHF FSASNSGNTA TLTISRVEAGSLKLSSVTAA DTAVYYCARR DEADYYCQVW DSSSDHVVFG AGILTGYLDS WGQGTLVTVSSGGTKLTVLGQ PKAAPSVTL HL161C  8 QVQLVQSGAE VKKPGASVKV 18DIQMTQSPSS LSASVGDRVT SCKASGYTFT GCYMHWVRQA ITCRASQGIS NYLAWFQQKPPGQGLEWMGR INPNSGGTNY GKAPKSLIYA ASSLQSGVPS AQKFQGRVTM TRDTSISTAYKFSGSGSGTD FTLTISSLQS MDLSRLRSDD TAVYYCARDY EDFATYYCQQ YDSYPPTFGGSGWSFDYWGQ GTLVTVSS GTKVEIKRTV AAPSVFI HL161D 10 QLQLQESGPG LVKPSETLSL20 SYELTQPLSV SVALGQTARI TCTVSGGSIS SSSYYWGWIR TCGGNNIGSK NVHWYQQKPGQPPGKGLEWI GNIYYSGSTY QAPVLVIYRD SNRPSGIPER YNPSLMSRVT ISVDTSKNQFFSGSNSGNTA TLTISRAQAG SLKLSSVTAA DTAVYYCARQ DEADYYCQVW DSSTVVFGGGLSYNWNDRLF DYWGQGTLVT TKLTVLGQPK AAPSVTL VSS

TABLE 3 CDR sequences of heavy-chain and light-chain variable domainsof selected human FcRn antibodies Heavy-chain variable domain CDRLight-chain variable domain CDR Antibody CDR1 CDR2 CDR3 CDR1 CDR2 CDR3SEQ ID NO. 21 22 23 24 25 26 HL161A SCVMT VISGSGGST TPWWLRSP GGNNIGSTSDDSDRPS VRDSSSDH YYADSVKG FFDY VH VI SEQ ID NO. 27 28 29 30 31 32 HL161BFSYWV TIYYSGNTY RAGILTGYL GGNNIGSKS DDSDRPS QVWDSSSD (HL161BK) YNPSLKSDS VH HVV SEQ ID NO. 33 34 35 36 37 38 HL161C GCYMH RINPNSGGT DYSGWSFDRASQGISNY AASSLQS QQYDSYPP NYAQKFQG Y LA TF SEQ ID NO. 39 40 41 42 43 44HL161D SYYWG NIYYSGSTY QLSYNWND GGNNIGSK RDSNRPS QVWDSSTV YNPSLMS RLFDYNVH V

Example 4: Measurement of Antigen Binding Affinity ofHL161A/HL161B/HL161C/HL161D Antibodies by SPR

The binding affinities of HL161A, HL161B, HL161C and HL161D antibodiesby SPR were measured by immobilizing water-soluble hFcRn as a ligandonto a Proteon GLC chip (Bio-Rad) and measuring the affinity. Kineticanalysis was performed using a Proteon XPR36 system. shFcRn wasimmobilized on a GLC chip, and an antibody sample was allowed to reactat a concentration of 5, and sensogram results were obtained. In kineticanalysis, a 1:1 Langmuir binding model was used, the analysis wasrepeated six times at each of pH 6.0 and pH 7.4, and the mean KD valuewas calculated. Following the immobilization step, the chip wasactivated under the conditions of EDAC/NHS 0.5×, 30 μL/min and 300 sec.For immobilization, shFcRn was diluted in acetate buffer (pH 5.5) toconcentrations of 2 μg/mL and 250 μL, and the dilution was allowed toflow on the chip at a rate of 30 μL/min. When an immobilization level of200-300 RU was reached, the reaction was stopped. Then, deactivation wasperformed using ethanolamine at a rate of 30 μL/min for 300 sec. Each ofthe HL161 antibodies was serially 2-fold diluted from a concentration of10 nM to 5 nM, 2.5 nM, 1.25 nM, 0.625 nM, 0.312 nM, etc., therebypreparing samples. Sample dilution was performed using 1×PBST (pH 7.4)or 1×PBST (pH 6.0) at each pH. For sample analysis, association wasperformed at 50 μL/min for 200 sec, and the dissociation step wasperformed at 50 μL/min for 600 sec, after which regeneration wasperformed using glycine buffer (pH 2.5) at 100 μL/min for 18 sec. Thekinetic analysis of each sample was repeated six times, and then themean antigen binding affinity (KD) was measured. The kinetic parametersof the antibodies, which resulted from the SPR analysis, are shown inTable 4 below (FIGS. 2A through 2H).

TABLE 4 Results of kinetic analysis of antibody by humanFcRn-immobilized SPR pH 6.0 pH 7.4 Antibody k_(on) (M⁻¹s⁻¹) K_(off)(s⁻¹) K_(D) (M) k_(on) (M⁻¹s⁻¹) K_(off) (s⁻¹) K_(D) (M) HL161A 1.81 ×10⁶ 3.26 × 10⁻⁴ 1.80 × 10⁻¹⁰ 1.32 × 10⁶ 3.27 × 10⁻⁴ 2.47 × 10⁻¹⁰ HL161B9.12 × 10⁵ 7.35 × 10⁻⁴ 8.07 × 10⁻¹⁰ 7.10 × 10⁵ 1.25 × 10⁻³ 1.76 × 10⁻⁹ HL161C 1.74 × 10⁶ 3.32 × 10⁻⁴ 1.91 × 10⁻¹⁰ 1.36 × 10⁶ 3.16 × 10⁻⁴ 2.32 ×10⁻¹⁰ HL161D 9.70 × 10⁵ 1.38 × 10⁻³ 1.43 × 10⁻⁹  6.99 × 10⁵ 1.24 × 10⁻³1.78 × 10⁻⁹  hIgG₁  3.2 × 10⁵  4.6 × 10⁻⁴  1.4 × 10⁻⁹  No binding Nobinding No binding

Example 5: Analysis of Binding of HL161A/HL161B Antibodies to Human FcRnby FACS

Using human FcRn-expressing stable HEK293 cells, binding to FcRn at eachpH was analyzed using a FACS system. The FcRn binding test using FACSwas performed in reaction buffer at pH 6.0 and pH 7.4. Specifically,100,000 human FcRn-expressing stable HEK293 cells were washed with PBSbuffer and centrifuged in a table microcentrifuge at 4500 rpm for 5minutes to obtain cell pellets. The antibody was added to 100 μl of pH6.0 or pH 7.4 PBS/10 mM EDTA. The remaining cells pellets were suspendedin reaction buffer, and cell counting was performed. 10 μL of the cellsuspension was added to a slide, and the number of the cells in the cellsuspension was counted in a TC10 system, after which the cell suspensionwas diluted with reaction buffer to a cell concentration of 2×10⁶cells/mL. Each antibody sample was diluted to 500 nM. For analysis at pH6.0, the dilution was diluted to 20 nM in a 96-well v-bottom plate, and50 μL of the dilution was added to each well. For analysis at pH 7.4,500 nM antibody sample was diluted by 3-fold serial dilution, andanalyzed at a concentration ranging from 250 nM to 0.11 nM. 50 μL of thecells diluted to 2×10⁶ cells/mL were added to each well and suspended.The plate was mounted in a rotator at 4° C. and rotated at an angle of15° and 10 rpm for 90 minutes. After completion of the reaction, theplate was taken out of the rotator and centrifuged at 2000 rpm for 10minutes, and the supernatant was removed. A488 anti-hIgG goat antibodywas diluted at 1:200 in reaction buffer, and 100 μL of the antibodydilution was added to each well and suspended.

Next, the plate was mounted again in a rotator at 4° C. and rotated atan angle of 15° and 10 rpm for 90 minutes. After completion of thereaction, the plate was taken out of the rotator and centrifuged at 2000rpm for 10 minutes, and the supernatant was removed. After the washingprocedure was performed once more, 100 μL of reaction buffer was addedto each well to dissolve the cell pellets, and the plate was transferredinto a blue test tube. Next, 200 μL of reaction buffer was added to eachwell, and then measurement was performed in FACS. The FACS measurementwas performed under the following conditions: FS 108 volts, SS 426volts, FL1 324 volts, FL2 300 volts. These cells were analyzed by FACSusing BD FACSDiva™ v6.1.3 software (BD Bioscience).

The results were expressed as Mean Fluorescence Intensity (MFI). At pH7.4 and a concentration of 0.11-250 nM, HL161A and HL171B antibodiesshowed EC50 (Effective Concentration 50%) values of 2.46 nM and 1.20 nM,respectively, as analyzed by 4 parameter logistic regression using theMFI values (FIG. 3). In addition, two antibodies showed similarresponses at pH 6.0 compared with results at pH 7.4 (data not shown).

Example 6: Analysis of Blocking Effects of HL161A/HL161B Antibodies byFACS

HEK293 cells that express hFcRn on the cell surface were treated withthe two antibodies analyzed for their binding affinity for cell surfacehuman FcRn, and the blocking effects of the antibodies were examinedbased on a reduction in the binding of Alexa-Fluo-488-labelled hIgG1.The analysis procedure was performed in the following manner.

2 mL of 1×TE was added to each type of naïve HEK293 cells and humanFcRn-overexpressing stable HEK293 cells, which were incubated in a 5%CO₂ incubator at 37° C. for 1 min. The cells were recovered from theflasks, and 8 mL of reaction buffer (pH 6.0) was added thereto, afterwhich the cells were transferred into a 50 mL comical tube. The cellsuspension was centrifuged at 2000 rpm for 5 minutes to remove thesupernatant, and 1 mL of reaction buffer (pH 6.0) was added to each cellpellet. Then, the cell suspension was transferred into a fresh 1.5 mLEppendorf tube. Next, the cell suspension was centrifuged at 4000 rpmfor 5 minutes, and the supernatant was removed. Then, reaction buffer(pH 6.0) was added to the remaining cell pellet, and the cell number ofthe cell suspension was counted. Finally, the cell suspension wasdiluted with reaction buffer to a cell concentration of 2.5×10⁶cells/mL.

Each antibody sample was diluted to 400 nM, and then diluted by 4-foldserial dilution in a 96-well v-bottom plate. 50 μL of the sample dilutedto a final concentration of 200 nM to 0.01 nM was added to each well.Then, 10 μL of Alex488-hIgG1 diluted with 1 μM reaction buffer (pH 6.0)was each well. Finally, 40 μL of cells diluted to a cell concentrationof 2.5×10⁶ cells/mL were added to each well and suspended. The plate wasmounted in a rotator at 4° C. and rotated at an angle of 15° and 10 rpmfor 90 minutes. After completion of the reaction, the plate was takenout of the rotator, and centrifuged at 2000 rpm for 10 minutes to removethe supernatant. 100 μL of reaction buffer was added to each well todissolve the cell pellets, and the plate was transferred into a bluetest tube. Then, 200 μL of reaction buffer was added to each well, andmeasurement was performed in FACS. The FACS measurement was performedunder the following conditions: FS 108 volts, SS 426 volts, FL1 324volts, FL2 300 volts. These cells were analyzed by FACS using BDFACSDiva™ v6.1.3 software (BD Bioscience). The results were expressed asmean fluorescence intensity (MFI). The MFI of the test group wasprocessed after subtracting the measured MFI value of the cells alone(background signal). The percentage of the MFI of thecompetitor-containing tube relative to 100% of a control tube (AlexaFluor 488 alone, and no competitor) was calculated.

${{Blocking}\mspace{14mu} (\%)} = {\left( \frac{\begin{matrix}{{{MFI}\mspace{14mu} {of}\mspace{14mu} {hFcRn}\mspace{14mu} {stable}\mspace{14mu} \left( {{Competitor} + {A\; 488} - {{hIgG}\; 1}} \right)} -} \\{{MFI}\mspace{14mu} {of}\mspace{14mu} {HEK}\; 293\mspace{14mu} \left( {{A\; 488} - {{hIgG}\; 1}} \right)}\end{matrix}}{\begin{matrix}{{{MFI}\mspace{14mu} {of}\mspace{14mu} {hFcRn}\mspace{14mu} {stable}\mspace{14mu} \left( {{A\; 488} - {{hIgG}\; 1}} \right)} -} \\{{MFI}\mspace{14mu} {of}\mspace{14mu} {HEK}\; 293\mspace{14mu} \left( {{A\; 488} - {{hIgG}\; 1}} \right)}\end{matrix}} \right) \times 100}$

When the MFI was lower than the MFI of the human IgG1competitor-containing tube, the competitor antibody was determined tohave high competition rate. Based on the measured blocking effects (%)of the HL161A and HL161B antibodies under the conditions of pH 6.0 andconcentration of 0.01-200 nM, 4-parameter logistic regression wasperformed. As a result, it was shown that the HL161A and HL161Bantibodies showed IC50 (Inhibitory Concentration 50%) values of 0.92 nMand 2.24 nM, respectively (FIG. 4).

Example 7: Test for Effects of HL161A/HL161B in mFcRn −/− hFCRNTransgenic 32 (Tg32) Mice

Human IgG was injected into human FcRn-expressing Tg32 (hFcRn+/+,hpβ2m+/+, mFcRn−/−, mpβ2m−/−) mice (Jackson Laboratory), and then HL161Aand HL161B together with human IgG were administered to the mice inorder to examine whether the antibodies would influence the catabolismof human IgG.

HL161A and HL161B antibodies and human IgG (Greencross, IVglobulinS)were dispensed for 4-day administration at dose of 5, 10 and 20 mg/kgand stored, and PBS (phosphate buffered saline) buffer (pH 7.4) was usedas a vehicle and a 20 mg/kg IgG1 control. Human FcRn Tg32 mice wereadapted for about 7 days and given water and feed ad libitum.Temperature (23±2° C.), humidity (55±5%) and 12-hr-light/12-hr-darkcycles were automatically controlled. Each animal group consisted of 4mice. To use human IgG as a tracer, biotin-conjugated hIgG was preparedusing a kit (Pierce, Cat#. 21327). At 0 hour, 5 mg/kg of biotin-hIgG and495 mg/kg of human IgG were administered intraperitoneally to saturateIgG in vivo. At 24, 48, 72 and 96 hours after administration ofbiotin-IgG, each drug was injected intraperitoneally at doses of 5, 10and 20 mg/kg once a day. For blood collection, the mice were lightlyanesthetized with Isoflurane (JW Pharmaceutical), and then blood wascollected from the retro-orbital plexus using a heparinizedMicro-hematocrit capillary tube (Fisher) at 24, 48, 72, 96, 120 and 168hours after administration of biotin-IgG. At 24, 48, 72 and 96 hours,the drug was administered after blood collection. Immediately after 0.1mL of whole blood was received in an Eppendorf tube, plasma wasseparated by centrifugation and stored in a deep freezer (Thermo) at−70° C. until analysis.

The level of biotin-hIgG1 in the collected blood was analyzed by ELISAin the following manner. 100 μl of Neutravidin (Pierce, 31000) was addedto a 96-well plate (Costar, Cat. No: 2592) to a concentration of 1.0μg/ml, and then coated at 4° C. for 16 hours. The plate was washed threetimes with buffer A (0.05% Tween-20, 10 mM PBS, pH 7.4), and thenincubated in 1% BSA-containing PBS (pH 7.4) buffer at room temperaturefor 2 hours. Next, the plate was washed three times with buffer A, andthen a Neutravidin plate was prepared with 0.5% BSA-containing PBS (pH7.4) buffer so as to correspond to 1 μg/ml. A blood sample was seriallydiluted 500-1000-fold in buffer B (100 mM MES, 150 mM NaCl, 0.5% BSAIgG-free, 0.05% Tween-20, pH 6.0), and 150 μl of the dilution was addedto each well of the plate. The added sample was allowed to react at roomtemperature for 1 hour. Next, the plate was washed three times withbuffer A, and then 200 μl of 1 nM HRP-conjugated anti-human IgG goatantibody was added to each well and incubated at 37° C. for 2 hours.Next, the plate was washed three times with ice cold buffer B, and then100 μl of the substrate solution tetramethylbenzidine (RnD, Cat. No:DY999) was added to each well and allowed to react at room temperaturefor 15 minutes. 50 μl of 1.0 M sulfuric acid solution (Samchun, Cat. No:S2129) was added to each well to stop the reaction, after which theabsorbance at 450 nm was measured.

The concentration of biotin-IgG after 24 hours (approximately Tmax ofbiotin-IgG in mice; before the occurrence of catabolism of biotin-IgG)was set at 100%, and the percentages of the concentration at other timepoints relative to the concentration at 24 hours were analyzed. Theresults of the analysis indicated that the half-lives of the vehicle andthe 20 mg/kg IgG1 control were 103 hours and 118 hours, respectively.However, the blood IgG half-life of the HL161A antibody, which showedexcellent human FcRn binding affinity and blocking effect in the invitro analysis and the fastest IgG catabolism in the human FcRntransgenic Tg32 mice, were 30, 23 and 18 hours at varying doses. Inaddition, the HL161B antibody showed IgG half-lives of 41, 22 and 21hours. This suggests that the pH-independent and Fc-non-competitiveantibodies for hFcRn have the effect of increasing the catabolism ofendogenous antibodies (FIGS. 5A and 5B).

Example 8: Test for Effects of HL161A/HL161B in Monkeys

Using cynomolgus monkeys having a homology of 96% to human FcRn, themonkey IgG, IgA, IgM and albumin levels by administration of the HL161Aand HL161B antibodies were analyzed, and the pharmacokinetics (PK)profiles of the antibodies were analyzed.

1) Analysis of Change in Expression of Immunoglobulin G in Monkey Blood

First, a change in monkey IgG was measured by ELISA analysis. 100 μL ofanti-human IgG Fc antibody (BethylLab, A80-104A) was loaded into eachwell of a 96-well plate (Costar, Cat. No: 2592) to a concentration of4.0 μg/mL, and then coated at 4° C. for 16 hours. The plate was washedthree times with washing buffer (0.05% Tween-20, 10 mM PBS, pH 7.4), andthen incubated with 1% BSA-containing PBS (pH7.4) buffer at roomtemperature for 2 hours. The standard monkey IgG was used at aconcentration of 3.9-500 ng/mL, and the blood sample was diluted80,000-fold in 1% BSA-containing PBS (pH7.4) buffer, and the dilutionwas loaded into the plate and incubated at room temperature for 2 hours.Next, the plate was washed three times with washing buffer, and then 100μL of a 20,000-fold dilution of anti-hIgG antibody (Biorad, 201005) wasloaded into the plate and allowed to react at room temperature for 1hour. After each plate was washed, 100 μL of the substrate solution3,3′,5,5′-tetramethylbenzidine (RnD, Cat. No: DY999) was loaded into theplate and allowed to react at room temperature for 7 minutes, afterwhich 50 μL of 1.0 M sulfuric acid solution (Samchun, Cat. No: S2129)was added to each well to stop the reaction. For analysis, absorbance(OD) was measured using a 450 nm and 540 nm absorbance reader (MD,Model: VersaMax). As a result, it was shown that, when each of theHL161A and HL161B antibodies was administered intravenously intocynomolgus monkey at doses of 5 and 20 mg/kg once a week, the monkey IgGlevel decreased in a dose-dependent manner, and the HL161 antibodieseffectively blocked the IgG-FcRn interaction. 5 mg/kg of HL161A reducedthe monkey IgG level to 47.1% on day 9, and 20 mg/kg of HL161A reducedthe monkey IgG level to 29.6% on day 10. 5 mg/kg of HL161B reduced themonkey IgG level to 53.6% on day 10, and 20 mg/kg of HL161B reduced themonkey IgG level to 31% on day 9, suggesting that the two antibodiesshowed similar results (Table 5 and FIGS. 6A through 6C). In addition,the change in monkey IgG level by intravenous administration of HL161Aand HL161B was compared between individuals, and as a result, it wasshown that the monkey IgG level was decreased between individuals in avery similar way.

TABLE 5 Change (%) in monkey IgG level by administration of HL161A andHL161B HL161A HL161B Day Vehicle 5 mg/kg 20 mg/kg 5 mg/kg 20 mg/kg 0 day100.0 ± 0.0  100.0 ± 0.0  100.0 ± 0.0  100.0 ± 0.0  100.0 ± 0.0  0.5 day99.0 ± 4.8 81.5 ± 1.8 101.5 ± 9.0  94.3 ± 5.4 96.2 ± 3.0 1 day  97.6 ±15.9 67.2 ± 2.0  86.2 ± 11.9  83.9 ± 24.7 94.1 ± 7.0 2 day 97.8 ± 6.263.0 ± 3.3 74.2 ± 14  73.7 ± 11.3 71.7 ± 5.4 3 day 104.5 ± 13.1 61.8 ±8.0  59.2 ± 11.0 68.3 ± 9.3 61.3 ± 6.0 4 day 100.9 ± 16.7 55.3 ± 4.145.1 ± 4.6  65.5 ± 12.2 44.3 ± 5.6 5 day 103.4 ± 12.5 60.8 ± 8.3 38.8 ±4.9  65.0 ± 11.9 38.4 ± 3.7 6 day 113.3 ± 8.5   64.9 ± 11.7 39.7 ± 6.4 66.4 ± 11.3 39.0 ± 5.4 7 day 116.9 ± 23.3 58.7 ± 4.7 39.6 ± 5.4 61.4 ±8.0 37.5 ± 3.2 7.5 day  92.4 ± 10.4 51.2 ± 7.2 38.7 ± 7.8 62.8 ± 8.339.3 ± 0.4 8 day 94.6 ± 8.7 48.0 ± 9.3 36.1 ± 5.3 60.7 ± 7.5 39.6 ± 5.99 day 117.6 ± 14.3 47.1 ± 4.4 33.8 ± 5.0 54.3 ± 6.9 31.0 ± 3.1 10 day115.1 ± 16.7 49.7 ± 8.9 29.6 ± 5.8 53.6 ± 4.9 32.8 ± 4.3 11 day 114.6 ±18.9 47.7 ± 4.2 30.4 ± 6.5 54.7 ± 4.2 39.9 ± 9.1 12 day 109.5 ± 13.151.7 ± 3.1 32.9 ± 5.7 56.5 ± 4.7 46.7 ± 9.1 13 day 111.1 ± 21.2 52.9 ±6.4 35.7 ± .2  58.7 ± 3.8 45.4 ± 7.6 14 day 128.9 ± 17.7 54.7 ± 4.2 37.8± 9.6 60.6 ± 4.2  53.8 ± 11.3 17 day 95.6 ± 6.6  59.5 ± 10.3 40.2 ± 7.456.7 ± 4.4  48.4 ± 10.0 20 day 92.5 ± 8.4 62.4 ± 6.7 47.6 ± 8.9 61.8 ±6.0 54.0 ± 9.5 23 day 107.1 ± 15.2 71.9 ± 6.5  61.8 ± 13.3 64.9 ± 4.456.8 ± 6.0 26 day 104.0 ± 5.6  77.7 ± 6.8  72.2 ± 22.4 70.8 ± 7.4 62.4 ±5.8 29 day 102.4 ± 8.3  81.4 ± 6.7  77.9 ± 20.5 74.8 ± 5.1  65.4 ± 10.8

2) Analysis of Pharmacokinetic Profiles of HL161A/HL161B in Monkey Blood

The time-dependent pharmacokinetic profiles (PK) of HL161A and HL161Bafter intravenous administration were analyzed by competitive ELISA.Specifically, a solution of 2 μg/mL of Neutravidin was prepared, and 100μL of the solution was coated on each well of a 96-well plate, and thenincubated at 4° C. for 18 hours. The plate was washed three time with300 μL of wash buffer (0.05% Tween 20 containing 10 mM PBS, pH 7.4), andthen each well was incubated with 1% BSA-containing PBS (pH 7.4) bufferat 25° C. for 2 hours. Biotinylated hFcRn was diluted with PBS to 1μg/mL, and then 100 μL of the dilution was added to each well of the96-well plate and incubated at 25° C. for 1 hour. Next, the plate waswashed three times with 300 μL of wash buffer to remove unbound hFcRn,and then a standard sample (0.156-20 ng/mL) was added to each well andincubated at 25° C. for 2 hours. Next, the plate was washed three timeswith wash buffer, and 100 μL of a 1:10,000 dilution of detectionantibody in PBS was added to each well and incubated at 25° C. for 1.5hours. The plate was finally washed three times, and 100 L of TMBsolution was added to each buffer and incubated at room temperature for5 minutes, after which 50 μL of 1M sulfuric acid as a reaction stopsolution was added to each well to stop the reaction. Next, theabsorbance at 450 nm was measured with a microplate reader. The analysisresults for HL161A and HL161B are shown in Table 6 below, and as can beseen therein, the pharmacokinetic profile of the antibodies increased ina dose-dependent manner. The half-life (T1/2) of the antibodies wasabout 6-12 days, which was shorter than that of generally knownantibodies. In addition, it was shown that the half-life, when observingoverally, AUC and Cmax of HL161B were higher than those of HL161A (FIGS.7A and 7B).

TABLE 6 Analysis results for pharmacokinetic profiles of HL161A andHL161B at varying doses Cmax AUC T_(1/2) Ab (Dose) Day (mg/ml) (mg/ml ·hr) (hr) HL161A 0-7 157 ± 31  1,601 ± 501 6.9 ± 0.9 (5 mg/kg)  7-14 157± 25  1,388 ± 334 10.3 ± 2.8  HL161A 0-7 692 ± 138 13,947 ± 2,459 9.0 ±0.6 (20 mg/kg)  7-14 724 ± 125 12,699 ± 2,114 7.6 ± 1.6 HL161B 0-7 178 ±56   2,551 ± 1,356 7.9 ± 1.3 (5 mg/kg)  7-14 187 ± 9  2,772 ± 466 9.4 ±0.5 HL161B 0-7 823 ± 38  21,867 ± 1,088 11.7 ± 1.0  (20 mg/kg)  7-14 868± 66  16,116 ± 1,501 6.8 ± 0.9

3) Analysis of Change in IgM and IgA Antibody Levels in Monkey Blood

ELISA analysis for measuring IgM and IgA levels in monkey blood wasperformed in a manner similar to the ELISA method for measuring IgGlevels. Specifically, 100 μL of anti-monkey IgM antibody (AlphaDiagnostic, 70033) or IgA antibody (Alpha Diagnostic, 70043) was addedto each well of a 96-well plate to a concentration of 2.0 μg/mL, andthen coated at 4° C. for 16 hours. The plate was washed three times withwash buffer (0.05% Tween-20 containing 10 mM PBS, pH 7.4), and thenincubated with 1% BSA-containing PBS (pH7.4) buffer at room temperaturefor 2 hours. The standard monkey IgM was analyzed at a concentration of7.8-1,000 ng/mL, and IgA was analyzed at 15.6-2,000 ng/mL. The bloodsample was diluted 10,000- or 20,000-fold in 1% BSA-containing PBS(pH7.4) buffer, and the dilution was added to each well and incubated atroom temperature for 2 hours. Next, the plate was washed three timeswith wash buffer, and then 100 μL of a 5,000-fold dilution of each ofanti-monkey IgM secondary antibody (Alpha Diagnostic, 70031) andanti-monkey IgA secondary antibody (KPL, 074-11-011) was added to eachwell and allowed to react at room temperature for 1 hour. The plate wasfinally washed three times, and 100 μL of the substrate solution3,3′,5,5′-tetramethylbenzidine (RnD, Cat. No: DY999) was added to eachwell and allowed to react at room temperature for 7 minutes. Next, 50 μLof 1.0 M sulfur solution (Samchun, Cat. No: S2129) was added to eachwell to stop the reaction. The absorbance of each well was measured witha 450 and 540 nm absorbance reader (MD, Model: VersaMax).

4) Analysis of Change in Albumin Levels in Monkey Blood

The analysis of a change in albumin levels in monkey blood was performedusing a commercial ELISA kit (Assaypro, Cat. No: EKA2201-1). Briefly,monkey serum as a test sample was 4000-fold diluted, and 25 μL of thedilution was added to each well of a 96-well plate coated with anantibody capable of binding to monkey albumin. 25 μL of biotinylatedmonkey albumin solution was added to each well and incubated at 25° C.for 2 hours. The plate was washed three times with 200 μL of washbuffer, and then 50 μL of a 1:100 dilution of streptavidin-peroxidaseconjugated antibody was added to each well and incubated at 25° C. for30 minutes. The plate was finally washed three times, and then 50 μL ofa substrate was added to each well and incubated at room temperature for10 minutes. Next, 50 μL of a reaction stop solution was added to eachwell, and the absorbance at 450 nm was measured. As a result, the clearchanges in monkey IgM, IgA and albumin levels by administration of theHL161A and HL161B antibodies were not observed throughout the testperiod (FIGS. 8A through 8C). Thus, it is concluded that the HL161antibody is involved only in IgG levels and does not influence thelevels of IgM and IgA, suggesting that it will have no significantinfluence on the decrease in immunity by a decrease in immunoglobulinlevels. In addition, no significant change in the monkey albumin levelwas observed throughout the test period, suggesting that the HL161A andHL161B antibodies specifically block only the IgG-FcRn interactions.

5) Analysis of Blood Biochemical Levels and Urinary Components

Finally, blood biochemical analysis and urinary analysis byadministration of the antibodies were performed using samples on day 14of the test. Blood biochemical markers, including aspartateaminotransferase (AST), alanine aminotransferase (ALT), alkalinephosphatase (ALP), creatine phosphokinase (CPK), total bilirubin (TBIL),glucose (GLU), total cholesterol (TCHO), triglyceride (TG), totalprotein (TP), albumin (Alb), albumin/globulin (A/G), blood urea nitrogen(BUN), creatinine (CRE), inorganic phosphorus (IP), calcium (Ca), sodium(Na), potassium (K) and chloride (Cl), were analyzed using the Hitachi7180 system. In addition, markers for urinary analysis, includingleukocyte (LEU), nitrate (NIT), urobilinogen (URO), protein (PRO), pH,occult blood (BLO), specific gravity (SG), ketone body (KET), nilirubin(BIL), glucose (GLU), and ascorbic acid (ASC), were analyzed using theMission U120 system. Although there were slight changes in the levels,the measured levels were included in the normal level ranges ofcynomolgus monkeys.

Example 9: hFcRn Co-Crystal Structure with HL161BK Antibody Fab

The X-ray crystal structure of human FcRn in complex with HL161BKantibody Fab fragment has been solved at 2.4 Å resolution. There are twocopies each of hFcRn and HL161BK Fab per asymmetric unit. Each hFcRnbinds to a single HL161BK antibody Fab, and complex formation buriesaround 1770 A2 of the solvent-accessible surface area. The complex wasgrown using the hanging drop method of vapour diffusion in a 24 wellplate with a precipitant solution containing 0.1 M Na Citrate pH 4.9 and14% PEG 6000. The crystal was cryo-cooled by transferring it to asolution containing 0.1 M Na Citrate pH 4.9, 18% PEG 6000 and 20%glycerol for ˜10 seconds before capturing it in a loop and plunging itinto liquid nitrogen. A data set was collected at ESRF beamline ID30A-1.Data processing in MOSFLM and AIMLESS (CCP4) indicated that the mostlikely space group was P21 with unit cell dimensions a=73.2 Å, b=140.2Å, c=95.2 Å and 3=92.9°, giving a total cell volume of 975531.56 Å.Using the program REFMAC5, the crystal structure was refined to anR_(work) of 24.7% (R_(free) of 30.5%) for the reflections between 94 Åand 2.4 Å.

The hFcRn specific residues or epitope interacting with HL161BK, definedat a distance ≦4.1 Å, were S15, S16, P17, P19, G20, A23, F24, S40, L41,R42, R69, E72, K73, F75, L76, F79, G84 and Y88 of α chain extracellulardomain and E36 from β2m chain (bolded). The hFcRn specific residues orepitope involved in the interface, defined as those with a maximumintermolecular distance between atoms of 5 Å, are 13-21, 23-24, 40-43,69, 72-73, 75-76, 79-80, 83-86 and 88 from α chain extracellular domainand 36 from β2m chain (underlined)

[hFcRn α chain extracellular sequence] SEQ ID NO: 45   1AESHLSLLYH LTAVSSPAPG TP AF WVSGWL GPQQYLSYN S LRGEAEPCGA  50  51WVWENQVSWY WEKETTDL R I K EK L FL EA FK ALGGKGP Y TL QGLLGCELGP 100 101DNTSVPTAKF ALNGEEFMNF DLKQGTWGGD WPEALAISQR WQQQDKAANK 150 151ELTFLLFSCP HRLREHLERG RGNLEWKEPP SMRLKARPSS PGFSVLTCSA 200 201FSFYPPELQL RFLRNGLAAG TGQGDFGPNS DGSFHASSSL TVKSGDEHHY  250 251CCIVQHAGLA QPLRVELESP AKSS [hFcRn β2m chain] SEQ ID NO: 46  1IQRTPKIQVY SRHPAENGKS NFLNCYVSGF HPSDI E VDLL KNGERIEKVE 50 51HSDLSFSKDW SFYLLYYTEF TPTEKDEYAC RVNHVTLSQP KIVKWDRDM

Although the present disclosure has been described in detail withreference to the specific features, it will be apparent to those skilledin the art that this description is only for purposes of illustrationand does not limit the scope of the present disclosure. Thus, thesubstantial scope of the present disclosure will be defined by theappended claims and equivalents thereof.

1. An isolated anti-FcRn antibody or a fragment thereof, comprising:CDR1 comprising one or more amino acid sequence selected from the groupconsisting of SEQ ID Nos: 21, 24, 27, 30, 33, 36, 39 and 42; CDR2comprising one or more amino acid sequence selected from the groupconsisting of SEQ ID Nos: 22, 25, 28, 31, 34, 37, 40 and 43; and CDR3comprising one or more amino acid sequence selected from the groupconsisting of SEQ ID Nos: 23, 26, 29, 32, 35, 38, 41 and
 44. 2. Theantibody or a fragment thereof according to claim 1, comprising: CDR1comprising amino acid sequence of SEQ ID No: 21, CDR2 comprising aminoacid sequence of SEQ ID No: 22 and CDR3 comprising amino acid sequenceof SEQ ID No: 23, CDR1 comprising amino acid sequence of SEQ ID No: 27,CDR2 comprising amino acid sequence of SEQ ID No: 28 and CDR3 comprisingamino acid sequence of SEQ ID No: 29, CDR1 comprising amino acidsequence of SEQ ID No: 33, CDR2 comprising amino acid sequence of SEQ IDNo: 34 and CDR3 comprising amino acid sequence of SEQ ID No: 35, or CDR1comprising amino acid sequence of SEQ ID No: 39, CDR2 comprising aminoacid sequence of SEQ ID No: 40 and CDR3 comprising amino acid sequenceof SEQ ID No:
 41. 3. The antibody or a fragment thereof according toclaim 1, comprising: CDR1 comprising amino acid sequence of SEQ ID No:24, CDR2 comprising amino acid sequence of SEQ ID No: 25 and CDR3comprising amino acid sequence of SEQ ID No: 26, CDR1 comprising aminoacid sequence of SEQ ID No: 30, CDR2 comprising amino acid sequence ofSEQ ID No: 31 and CDR3 comprising amino acid sequence of SEQ ID No: 32,CDR1 comprising amino acid sequence of SEQ ID No: 36, CDR2 comprisingamino acid sequence of SEQ ID No: 37 and CDR3 comprising amino acidsequence of SEQ ID No: 38, or CDR1 comprising amino acid sequence of SEQID No: 42, CDR2 comprising amino acid sequence of SEQ ID No: 43 and CDR3comprising amino acid sequence of SEQ ID No:
 44. 4. The antibody or afragment thereof according to claim 1, comprising one or more heavychain variable regions and light chain variable regions selected fromthe group consisting of: heavy chain variable region comprising CDR1comprising amino acid sequence of SEQ ID No: 21, CDR2 comprising aminoacid sequence of SEQ ID No: 22 and CDR3 comprising amino acid sequenceof SEQ ID No: 23, and light chain variable region comprising CDR1comprising amino acid sequence of SEQ ID No: 24, CDR2 comprising aminoacid sequence of SEQ ID No: 25 and CDR3 comprising amino acid sequenceof SEQ ID No: 26; heavy chain variable region comprising CDR1 comprisingamino acid sequence of SEQ ID No: 27, CDR2 comprising amino acidsequence of SEQ ID No: 28 and CDR3 comprising amino acid sequence of SEQID No: 29, and light chain variable region comprising CDR1 comprisingamino acid sequence of SEQ ID No: 30, CDR2 comprising amino acidsequence of SEQ ID No: 31 and CDR3 comprising amino acid sequence of SEQID No: 32; heavy chain variable region comprising CDR1 comprising aminoacid sequence of SEQ ID No: 33, CDR2 comprising amino acid sequence ofSEQ ID No: 34 and CDR3 comprising amino acid sequence of SEQ ID No: 35,and light chain variable region comprising CDR1 comprising amino acidsequence of SEQ ID No: 36, CDR2 comprising amino acid sequence of SEQ IDNo: 37 and CDR3 comprising amino acid sequence of SEQ ID No: 38; andheavy chain variable region comprising CDR1 comprising amino acidsequence of SEQ ID No: 39, CDR2 comprising amino acid sequence of SEQ IDNo: 40 and CDR3 comprising amino acid sequence of SEQ ID No: 41, andlight chain variable region comprising CDR1 comprising amino acidsequence of SEQ ID No: 42, CDR2 comprising amino acid sequence of SEQ IDNo: 43 and CDR3 comprising amino acid sequence of SEQ ID No:
 44. 5. Anisolated anti-FcRn antibody, comprising: CDR1 comprising amino acidsequence, which has at least 90% homology with one or more amino acidsequence selected from the group consisting of SEQ ID Nos: 21, 24, 27,30, 33, 36, 39 and 42; CDR2 comprising amino acid sequence, which has atleast 90% homology with one or more amino acid sequence selected fromthe group consisting of SEQ ID Nos: 22, 25, 28, 31, 34, 37, 40 and 43;and CDR3 comprising amino acid sequence, which has at least 90% homologywith one or more amino acid sequence selected from the group consistingof SEQ ID Nos: 23, 26, 29, 32, 35, 38, 41 and 44, or a fragment thereof.6. An isolated anti-FcRn antibody or a fragment thereof, comprising oneor more heavy chain variable regions and light chain variable regionscomprising one or more amino acid sequences selected from the groupconsisting of amino acid sequences of SEQ ID Nos: 2, 4, 6, 8, 10, 12,14, 16, 18 and
 20. 7. The antibody or a fragment thereof according toclaim 6, comprising a heavy chain variable region comprising an aminoacid sequence of SEQ ID Nos: 2, 4, 6, 8, or
 10. 8. The antibody or afragment thereof according to claim 6, comprising a light chain variableregion comprising an amino acid sequence of SEQ ID Nos: 12, 14, 16, 18or
 20. 9. The antibody or a fragment thereof according to claim 6,comprising one or more heavy chain variable regions and light chainvariable regions selected from the group consisting of: heavy chainvariable region comprising amino acid sequence of SEQ ID No: 2 and lightchain variable region comprising amino acid sequence of SEQ ID No: 12;heavy chain variable region comprising amino acid sequence of SEQ ID No:4 and light chain variable region comprising amino acid sequence of SEQID No: 14; heavy chain variable region comprising amino acid sequence ofSEQ ID No: 6 and light chain variable region comprising amino acidsequence of SEQ ID No: 16; heavy chain variable region comprising aminoacid sequence of SEQ ID No: 8 and light chain variable region comprisingamino acid sequence of SEQ ID No: 18; and heavy chain variable regioncomprising amino acid sequence of SEQ ID No: 10 and light chain variableregion comprising amino acid sequence of SEQ ID No:
 20. 10. An isolatedanti-FcRn antibody or a fragment thereof, comprising one or more heavychain variable regions and light chain variable regions comprising aminoacid sequence, which has at least 90% homology with one or more aminoacid sequences selected from the group consisting of amino acidsequences of SEQ ID Nos: 2, 4, 6, 8, 10, 12, 14, 16, 18 and
 20. 11. Theantibody or a fragment thereof according to claim 1, wherein theantibody binds FcRn with a KD (dissociation constant) value of 0.01 to 2nM, at pH 6.0 or pH 7.4 condition.
 12. The antibody or a fragmentthereof according to claim 1, wherein the antibody is monoclonalantibody, murine antibody, chimeric antibody, humanized antibody orhuman antibody.
 13. The antibody or a fragment thereof according toclaim 1, wherein the antibody or fragment thereof comprises full-lengthantibodies, Fab, F(ab′)2, Fd, Fv, scFv, domain antibodies, dual-specificantibodies, bibodies, minibodies, tribodies, scap (sterol regulatorybinding protein cleavage activating protein), bispecific antibodies,trispecific antibodies, multispecific antibodies, diabodies, triabodies,tetrabodies, intrabodies, nanobodies, small modularimmunopharmaceuticals (SMIP), binding-domain immunoglobulin fusionproteins, camelized antibodies or VHH containing antibodies.
 14. Theantibody or a fragment thereof according to claim 1, wherein theantibody comprises IgD antibodies, IgE antibodies, IgM antibodies, IgG1antibodies, IgG2 antibodies, IgG3 antibodies, IgG4 antibodies.
 15. Apolynucleotide encoding the antibody or a fragment thereof according toclaim
 1. 16. A polynucleotide encoding an anti-FcRn antibody or afragment thereof, comprising one or more sequence selected from thegroup consisting of SEQ ID Nos: 1, 3, 5, 7, 9, 11, 13, 15, 17 and 19.17. A polynucleotide encoding an anti-FcRn antibody or a fragmentthereof, comprising sequence which has at least 90% homology with one ormore sequence selected from the group consisting of SEQ ID Nos: 1, 3, 5,7, 9, 11, 13, 15, 17 and
 19. 18. A recombinant expression vector,comprising the polynucleotide according to claim
 15. 19. A host cell,which is transected with the recombinant expression vector of claim 18.20. A method of preparing an anti-FcRn antibody or a fragment thereof,comprising: culturing the host cell of claim 19 and producing theantibody therefrom; and isolating and purifying the produced antibody torecover the antibody binding specifically to FcRn.
 21. A pharmaceuticalcomposition comprising the antibody or a fragment thereof according toclaim 1, and one or more pharmaceutically acceptable carrier.
 22. Amethod of treating a patient suffering from an autoimmune disease,comprising administering the composition of claim 21 to said patient.23. The method of claim 22, wherein the autoimmune disease is oneselected from the group consisting of immune neutropenia, Guillain-Barrésyndrome, epilepsy, autoimmune encephalitis, Isaac's syndrome, nevussyndrome, pemphigus vulgaris, Pemphigus foliaceus, Bullous pemphigoid,epidermolysis bullosa acquisita, pemphigoid gestationis, mucous membranepemphigoid, antiphospholipid syndrome, autoimmune anemia, autoimmuneGrave's disease, Goodpasture's syndrome, myasthenia gravis, multiplesclerosis, rheumatoid arthritis, lupus, idiopathic thrombocytopenicpurpura, lupus nephritis and membranous nephropathy.
 24. A compositioncomprising the antibody or a fragment thereof according to claim 1,labelled with a detection label.
 25. A method of detecting FcRn in vivoor in vitro, comprising using the antibody or a fragment thereofaccording to claim
 1. 26. An isolated anti-FcRn antibody or a fragmentthereof, which binds to an epitope of human FcRn comprising residuesS15, S16, P17, P19, G20, A23, F24, S40, L41, R42, R69, E72, K73, F75,L76, F79, G84 and Y88 of α chain extracellular domain (SEQ ID NO:45) andE36 from β2m chain (SEQ ID NO:46).
 27. The antibody or a fragmentthereof according to claim 26, which binds to further one or moreresidues selected from the group consisting of A13, V14, A18, T21, G43,K80, G83, K85 and G86 of α chain extracellular domain (SEQ ID NO:45).